The reproductive stages of corn are often over looked and not fully understood, but as discussions of fungicide applications, maximizing yield and monitoring grain development continue, having a basic understanding will help make better production decisions:

Corn reproductive stages generally consume 60 days starting with silk emergence and ending at black layer.  There are six recognized growth stages during the reproductive stages and are designated with an “R,” followed by a number designating subsequent stages. 

R1: Silking

R2: Blister

R3: Milk

R4: Dough

R5: Dent

R6: Physiological Maturity

Silking (R1) begins when silks emerge from the ear and are ready to receive pollen.

Blister (R2) stage begins 10 to 14 days after silking begins and the kernels are whitish blisters and contain a clear liquid if busted.  By this point the silks are brown and drying rapidly.  R2 is also often referred to as the “Brown Silk Stage.”  Starch begins to accumulate in the kernel while the radicle root, coleoptile and first leaf have formed in the embryo.

Milk (R3) stage begins 18 – 22 days after silking.  R3 is commonly referred to as the roasting ear stage.  The kernels are mostly yellow or dull yellow and filled with milky white fluid.  By the R3 stage the ear kernel number is generally determined and additional kernel loss will be minimal.

Dough (R4) stage begins 24 – 28 days after silking.  The kernel’s milky fluid is changing to a “dough” consistency as starch accumulation.  The kernels are gaining consistency and size and the color is becoming more yellow and could develop a small dent in the kernel.  Stress during this period will not lead to kernel loss, but will primarily affect the kernel weight.  The cob is beginning to show some color from light red to pink.

Dent (R5) occurs 35 – 42 days after silking and all kernels have fully dented and the hard starch begins forming at the top of the kernel.  The best way to recognize and identify this stage is to look for the top of the kernel turning bright, shinny, dark yellow color and the inside of the kernel is of a firm consistency.  Kernels will continue to fill and add weight for another 20 days and hot dry weather can still reduce yields by 15-20% during this stage.

Dent stage also is when the “milk line” can be seen.  The milk line is the separation between the liquid and solid starch areas of the kernel.  As the kernel continues toward maturation the milk line moves from the tip to the top of the kernel.

Physiological Maturity (R6) starts 55 to 65 days after silking and is often referred to as “black layer.”  Physiological maturity occurs shortly after the milk line disappears and just before the formation of the black layer at the tip of the kernel.

Source:

http://www.mississippi-crops.com/2017/05/31/identifying-corn-reproductive-growth-stages-and-management-implications/

https://www.agry.purdue.edu/ext/corn/news/timeless/GrainFill.pdf

Growers of non-gmo corn, white corn, and waxy corn have struggled for years to predict where unwanted pollen might come from.  Now growers of IP yellow and white corn near fields of Enogen® corn are doing this as well.  Most pollen falls in the field it came from.  Yet, with only a 15-mph wind, pollen can travel as far as ½ mile within a couple of minutes while it is still viable (Nielsen, 2016). After discussing this challenge with Dr. Mark Westgate, Iowa State Professor of Agronomy, he directed me to a website developed by a fellow ISU professor, Daryl Herzmann.  The website shows detailed information of wind speed, direction, and duration in a diagram called a Wind Rose.

This article will help guide you through using the website so you can develop a wind rose for your fields.  The wind data comes from airports around the Midwest.  You will be able to choose the location you use.    

Gather Information

Before going to the website, it is helpful to gather some information.  First map out where the fields you are concerned about, I call them the “target” fields, are located.  You will have hybrid and planting date information on those fields.  You will need information on what corn is planted near your target fields.  You will want to know what hybrids and when they were planted.  You need to go at least ½ mile away on all sides of the target field.  Don’t assume the wind only comes from the south or west in the summer.

Calculating Pollination Window

Once you have the hybrid and planting information you will need to calculate silk emergence in your target field.  This can be estimated by using Growing Degree Unit (GDU) data and the data from your hybrid profile for GDUs to Mid-Pollen.  GDU data can be calculated from several websites/apps or gotten from Advantage Acre® if you are a subscriber.   For example, A6499 is 1362 GDUs to Mid-Pollen from the AgriGold Hybrid Profile Guide.  Using the Advantage Acre timeline, I can find what date that occurred on.  If you use a GDU calculator you can estimate that date as well.  Pollen shed is normally a two-week process, so go one week to both sides of the mid-pollen date to determine your silk exposure window.  If your corn field had uneven emergence and/or replant you may want to widen that window.

You have now determined the time period you are concerned about the wind.  However, if you want to refine your time period you can add the information about the surrounding fields.  By going through the same process, you can determine the pollen shed windows for those fields.  Then you can overlap the pollination windows to possibly narrow the time period you are concerned about.  Offsetting planting dates is a good away to lessen the risk of cross pollination.

Now you are ready to go to the website.  The directions will walk you through step-by-step on how to use it.

IEM Site
http://mesonet.agron.iastate.edu/sites/locate.php

This example is for the AgriGold office near Lawrenceville, IL for a period last summer. (Click on image 4).

Select By Network – From drop down select “state” ASOS.  If in Iowa Select “Iowa AWOS”  Click “Switch Network” button.

Select By Station – Select nearest location to your target field from map or drop down list.  Click “Select Station” button. (Click on image 5).

Click on “*Custom Wind Roses” tab. (Click on image 6).

Select Start/End Time:

Start:     Select Year, Month, Day, Hour (Beginning date of your calculated time period)
End:       Select Year, Month, Day, Hour (Ending date of you calculated time period)

Check box by #3. Limit to Range of hours given by start and end time.  Pollen usually sheds in the morning to early afternoon.  Try using 8:00 AM to 2:00 PM.

Direction Bins: Change to 24.  You can experiment with this.  Fewer bins consolidates wind the readings.

Image Format: Change to Portable Document Format (>PDF).  This will make Wind Rose easier to print.

Click “Submit” button.  Wind Rose will generate after a brief moment. (Click on image 7).

Interpreting your Wind Rose

• Imagine your target field as the center point of the wind rose.  The wind is blowing in to the center.
• Each triangle represents a wind direction during the designated time period.
• Wind speed is designated by color key at the bottom.
• Wind direction is designated on the outside perimeter.
• Frequency (%) of speed and direction is designated by the concentric circles.  Each wind rose may have different frequency scale.

Example: The red circled triangle tells us there was a period of wind from the NNE approximately 9% of the time period.  Approximately 5% of the time period the wind was NNE at 20+ mph.  Approximately 1.5% of the time period the wind was NNE at 15-20 mph.  The remaining 2.5% of the time period the wind was NNE at 10-15 mph.  This adds up to the 9%.

How can you use this information to help you lessen the risk from contamination causing the corn to be rejected and not qualifying for a premium?  Hopefully now you have a clearer picture of what parts of your target fields have possible issues.  Standard harvest procedure for IP corn fields is to harvest border rows all the way around the field and store separate from your IP corn.  If your isolation distance is less than 165 feet, the recommendation is to harvest 16 border rows.  If the isolation distance is between 165 feet and 660 feet, the recommendation is to harvest 8 rows (Thomison and Geyer, 2016).  The wind rose could help you modify border row harvest to reflect possible risk areas.  I recommend harvesting a minimum of 8 rows whether there is any perceived risk or not.

For those who have their own weather stations with recordable wind information there may be an option to use that with a different website or software.  I am currently working on that with a wind logger at a field near me.  When I get that figured out I will put out another article.

I hope this information can help lessen the risk of mixing contaminated corn with your IP corn.  If you have questions about this article, please contact me.  If you have questions about the website you can contact Daryl Herzmann at ISU.  Our contact information is below.

Chuck Hill - AgriGold - Specialty Products Manager, Chuck.hill@agrigold.com, 217.473.6063, Twitter @agold_chuck

Daryl Herzmann - Iowa State University - Analyst, akrherz@iastate.edu, 515.294.5978

Enogen® is a registered trademark of Syngenta Seeds, Inc.

Advantage Acre® is a registered trademark of AgReliant Genetics LLC
Nielsen, Bob. 2016. Tassel Emergence & Pollen Shed.  Purdue University
Peter Thomison and Allen Geyer. 2016. Managing “Pollen Drift” to Minimize Contamination of Non-GMO Corn.  The Ohio State University

Recent reports from the field have come in with corn literally falling over throughout the corn field.  One day the plants look healthy and growing and the next day they are falling over.  The surprise and concern over this will cause a grower to ask, “what is happening and why?”

When the plants that have fallen over are dug up, they are missing a very important part of their anatomy, their roots!  The phenomenon that causes corn plants to lose their roots is called Rootless Corn Syndrome or “Floppy Corn.”  There are really two main reasons for rootless corn syndrome to invade a corn field.  The first reason is in response to dry soil conditions and perfect timing with young corn plants that are trying to establish their nodal roots systems.  The syndrome usually starts following some wet periods and/or planting into soil still a little on the damp side in the spring, then soils has dried out down to the crown where nodal roots are initiated near the V3-V4 growth stage. Typically the nodal roots will grow downward in response to gravity as long as soil conditions, including moisture, are hospitable. If these roots elongate into dry surface soils they run the risk of drying out before finding moisture and dying. When the nodal roots die, the young plant must survive on seminal root contributions and anything left in the seed energy reserves until later nodal roots find their way to moisture. Normally, the seedling is fed by seed reserves and the seminal root system until the nodal roots take over around V5 to V6. "Floppy" corn is observed when seedlings without normal nodal root formation are tipped over from lack of support.  In severe cases, plants may lay down completely on the soil surface and the mesocotyl breaks leading to a dead plant.

 The second reason for Rootless Corn Syndrome to be present is caused by shallow planting.  When planting less than 1 – 1 ½” the soil can settle leaving the seed very near the soil surface.  As the seed germinates and begins to grow and tries to send out it’s nodal roots, they are extremely close to the soil surface.  If the soil surface happens to be dry and hot, the new roots will die and the above portion of the corn plant continues to grow as mentioned earlier and the plant falls over due to a lack of rooting strength.

There are no rescue measures for a field experiencing Rootless or Floppy Corn Syndrome, other than rain to rewet and cool the top 2” of soil so the plant can reestablish their nodal roots and straighten itself up.  If the soil conditions continue to be hot and dry for too long, the plant will run out of energy reserves and die.

During the early summer when corn is just starting to really grow fast, you can look out over a field and see some random yellow plants scattered throughout the field.  Often the first reaction is, “Wonder what they sprayed on that?” or “I wonder what’s wrong with those plants?”  The simple answer is those plants were not affected by any chemical and there is nothing wrong with them, other than they are growing faster than the plant can unwrap itself.

Rapid Growth Syndrome causes plants to literally wrap themselves up tight and have twisted whorls. Growers typically begin seeing twisted whorls at V5 to V6 corn. The lower most leaves are normal with the sixth or seventh leaf tightly wrapped, as if the rolled leaf has lost its elasticity. Young leaves inside the whorl continues to grow but are unable to emerge through the wrapped upper leaves. This continued growth creates pressure which causes the whorl to bend or kink at right angles to the ground.  The cause is typically due to an abrupt transition from slow growing conditions (cool, cloudy days) to rapid development (warm, sunny conditions).

In most cases these whorls will eventually open up and growth will resume normally with no yield loss expected. As these wrapped leaves open up, yellow leaves will become apparent across the field. A few days of sunshine will green them up and the problem will no longer be visible, except for a few crinkled leaf edges left behind caused by their restricted expansion inside the twisted whorl.  There is no yield loss associated with Rapid Growth Syndrome and in a couple of days those yellow leaves will turn green and all evidence will be gone.

The recent extended cool wet periods have caused many corn fields to need to be replanted due to less than ideal stands.  The saturated soils, crust and cold temperatures greatly decreased the viability of the corn seed that was plant 3-4 weeks ago.  Fortunately not all the corn stands failed and many fields were left, although the stands were not ideal, they were still acceptable for maintaining high yield potential.  Those fields survived the first round of stand establishment concerns, but, recent phone calls and evaluations from the field have led many corn fields into the next challenge in stand establishment: seedling blights. 

Seedling blights is the term used to describe corn plants that have been attacked by soil borne pathogens during the critical stage of emergence to V3.  The soil pathogens are present in every soil and are designed to decompose any plant material that is present in the soil.  A healthy growing corn plant’s natural defense against these seedling blight pathogens is rapid growth.  If the corn plant is able to grow faster than it can be attacked, the corn plant wins.  But, if the corn plant cannot grow faster than the attack, the pathogens win.  The seed treatment that comes on every bag is designed to help the corn plant have a 14-21 day window of protection, to germinate and outgrow these pests.  But after that window of opportunity, the corn plant is on its own.

Seedling blight pathogens thrive in cool, wet soils, the same environment that causes corn growth to be slow to non-existent.  The last 3-4 week window has been a perfect environment for seedling blight attacks and the corn has been sluggish long enough to be in the cross hairs for infection.

Scouting for seedling blights is relatively simple.  The first signs of seedling blights will show on the mesocotyl.  The mesocotyl is the part of the corn plant that attaches the seed to the above ground portion of the corn plant.  The mesocotyl is the umbilical cord that connects the new plant to its food source, the seed.  An infected mesocotyl will have brown lesions or be completely brown.  Once the mesocotyl turns brown and shrivels up, the young corn plant can no longer receive water and nutrients to survive.  Often the plants look healthy above ground one day and the next they are wilted and struggling, this is the above ground symptoms of the below ground problem with seedling blights.

Until the corn plant has reached the V3-V4 growth stage, it is solely dependent on the seed for its survival, after V3 it begins to grow its nodal roots that will provide the water and nutrients for further growth.  Therefore once the corn plant is living off its own roots, the seedling blight pathogens are no longer a concern for the corn plants survival. 

The corn crop is maturing quickly across the state and with maturity comes some unique and different events occurring out in the corn field.  There are currently three events, stalk quality issues, diplodia stalk rot and inconsistent ear size, that have peaked many growers interest and may need a little more explanation and insight.

Stalk Quality Issues:

There are few things in a corn grower’s life that are more frustrating than down corn.  Down corn is difficult and very time consuming to harvest and really tries patience and tempers.  The goal is always to have corn standing at harvest, but unfortunately it is not always possible.

Stalk quality issues are showing up in most of the April planted corn fields and will be showing up in the late May planted corn fields shortly.  How and why they are showing up is very important to understand. Simply put the corn plants only goal is to produce an ear of corn, period.  Therefore the corn plant will do whatever is necessary to ensure that an ear is produced.  During this grain fill period (the time after pollination to black layer) all corn has gone through some type of serve stress (drought, heat and/or too much water) and through that stress the corn plant still needed to provide nutrition for the corn ear, so it robbed it from the stalk and the roots.  Once the corn plant runs short on nutrients (water included) it shuts down its defense mechanisms to conserve resources.  Once the defenses are down, root rot pathogens quickly begin invading the roots and move up the stalk.  Once into the stalk the pathogens attack the nodes and stop the movement of water and other nutrients from moving within the plant.  This process leads to stalks being cannibalized and damaged and leaving the corn crop at risk for falling or being blown down.

By doing a quick survey in a field a grower can determine the amount of stalk damage that is present to aid in harvest timing questions.  By walking through the field and “pinching” the lower stalk, a grower can determine the strength of the stalks.  Also a simple “push” test can be performed by pushing the stalks to a 45⁰ angle and if the stalks return upright they are okay, but if they continue to fall over, stalk quality is a concern.  If more than 25% of the stalks shows stalk quality issues, early harvest should be considered to ensure the best harvetability possible.

Diplodia Ear Rot:

Diplodia ear rot is a relative easy ear rot to recognize.  The husks will be a bleached and/or brownish color.  Inside the husk, the ear will have a grayish-white to grayish brown mold on and between the kernels.  Typically the mold will begin at the bottom of the ear and will its way to the tip.  Occasionally the mold will start at the middle or top of the ear.

Diplodia overwinters on corn residue and is the source of infection.  Corn is also the only host for Diplodia ear rot pathogens.  The infection occurs when the spores are transferred either by rain or wind from the soil up to the ear.  Typically dry weather followed by wet conditions around silking most favor Diplodia infection.

There are no mycotoxins or vomitoxins associated with Diplodia ear rot.

The lighter kernels associated with this disease will lower the test weight of the grain.  Also due to the lightweight and fragile nature of Diplodia infected ears, more cobs and kernels will tend to ground up and/or present in the grain sample.  There is also a concern with fines being created with more handling through grain systems that can interfere with airflow during aeration.

To improve storability of the grain, dry the grain below 14% moisture and cool it below 50⁰ as quickly as possible.  Keep grain stored during the cold months of the year and have it removed prior to summer.

The best practice to eliminate the disease for the future is to use tillage to decompose the corn residue to eliminate its host.

Sporadic Ear Size in April Planted Corn:

Driving down the road and looking at corn fields during May, growers could of gotten a false sense of how uniformly their corn field actually emerged.  Most of all the corn fields that were planted in April looked similar to the field in the picture.  Driving down the road, it looked uniform and appeared that the emergence was more than acceptable.  Unfortunately upon a closer examination of the field, there were many plants that did not emerge uniformly and many fields took 2-4 weeks for complete emergence to occur.  Upon closer examination, growers would have seen plants that look like those in close up picture. While the plant count was there at the end, the true meaning of this sporadic emergence was not fully seen until ears began to develop.  Emergence timing is critical to the plant determining how large of an ear and factory it will produce.  The first plant that emerges carries the potential for the largest ear while the last plant to emerge produces the smallest ear.  All the plants that emerge between the first and last will continually decrease in size.  The resulting effect of non-uniform emergence is showing up ahead of combines with a large variation in ear size within a row.  The following picture is very typical of what growers are experiencing as they walk their April planted corn. 

The rate of growth for corn is temperature dependent.  The way we relate temperature to corn growth and development is through Growing Degree Unit’s (GDU’s).  Each growth stage can be estimated by calculating GDU’s, along with when we expect corn to reach physiological maturity and reach a harvest moisture goal.

To figure GDU’s, there is a simple calculation (Figure 1). 

·         Use formula from Steinacher’s Early Emergence GDU newsletter from 4-22-15

-Tmax or maximum temperature is should not exceed 86 degrees Farenheit.                                                    

-Tmin or minimum temperature does not go below 50 degrees Farenheit.

Once the corn plant transitions from the vegetative stage to the reproductive stage, it then utilizes nutrients for reproduction and no longer for plant growth.  Since the ear size has been determined, grain fill becomes the main priority.  Any stress, temperature, moisture or nutrient, will affect the size and weight of the kernels.  Once a corn plant reaches R6, or physiological maturity, the kernel moisture is 30-35% and will begin the drydown process.

References:

http://www2.ca.uky.edu/agcomm/pubs/agr/agr202/agr202.pdf

http://agron-www.agron.iastate.edu/Courses/agron212/Calculations/GDD.htm

During the past week rainfall has fallen across many dry and stressed corn acres.  The question has been asked, “Is this rain going to do any good?”  The simple answer is yes, it will.  If the corn plant has not died or dropped its ear, there will be good to come from this mid-August rain event. 

Why and how will it help?  The simplified yield equation is number of ears per acre x number of kernels per ear x kernel weight.  The first two, number of ears and number of kernels has already been determined and will not change drastically; therefore the last piece of the yield equation is how yield is increased with the recent rainfall.

Below is a chart that shows the daily water usage rate for corn during different growth stages.  Currently corn planted in April would fall in the full dent arena; while May planted corn would fall between the blister and beginning dent stage.  While the water use rate is decreasing there still is considerable demand as that corn plant is producing starch to build the kernel.

The next piece of the puzzle in determining if the August rainfall events will help yield, is to look at the nutrient uptake of the corn plant.  The logic behind the madness is if the corn plant is still taking up nutrients, but the corn plant itself is not growing, then where are the nutrients going?  The kernel!  The chart clearly shows that maximum nutrient uptake is not reached until black layer.  Nutrients such as nitrogen and sulfur still have a steep uptake curve because these nutrients are critical for starch and protein production in the kernel.  Also the main avenue for nutrient uptake in the corn is via the roots through water.  So the addition of water to the soil, will allow nutrients to go into solution and be readily available for uptake into the corn plant during this critical period of grain fill.

The final piece of the puzzle is the kernel dry matter accumulation.  The following chart demonstrates the % of kernel dry matter accumulation during the different reproductive stages.  Dry matter accumulation in the kernel is the greatest during dent, followed by the combination of milk and dough stages.  

Therefore as long as the corn is not black layered or mature, there is the possibility for the corn plant to add more starch to the kernels, thus increasing the final kernel weight and ultimately increasing the final yield of the entire corn field.  The saying “rain makes grain” is true all the way to the end!

Now that we are approaching Fall and every effort has been made to produce a great corn crop, it’s time to evaluate what’s in the field.  Probably the easiest method at this point in time requires little more than counting and being able to establish a realistic ear and field average.  Before we go any further though, this method should only be used if the corn field being evaluated is well into the R3 or Milk Stage (kernels are visibly yellow).  This is critical for the fact that prior to this stage kernels going through stress could still be aborted, thus throwing off counts.

1.     In 1/1000^th of an acre, count harvestable ears; excluding nubbins, dropped ears, severely lodged plants, &/or abnormal ears

2.     Count kernel rows on every 7^th ear

3.     Count kernels per row on those same ears, excluding the small 3-4 tip kernels

4.     Multiply harvestable ears X Average kernel rows X Average row length, then divide by thousands of kernels per bushel.

5.     Repeat these steps in several areas of the field for better estimates

Example: In 1/1000^th of an acre there are 30 harvestable ears with counts that average 16 rows around by 38 kernels long, normal fill conditions are expected for an average kernel sized variety.  (30 X 16 X 38) /90 = 202.67 Bu/A

One thing that could render this method’s results either too high or too low are the conditions during the rest of grain fill.  Better conditions than expected - like we were blessed with last year, provided for larger, heavier kernels. If we’d have known what our ending grain product would have been like it would have prompted us to divide by a factor closer to 80 or 85 when estimating yields.  On the opposite end of things, more rapid movement through reproductive stages because of stress will give us smaller kernels and a factor closer to 95 or 100 would give us a closer estimate.

     Regardless of how perfectly green fields look from the outside, or how many reports tell us things are ideal, the only true way to grasp what you have is to dive right in and start counting.

Recent rain events across the state have slowed, halted and even delayed the planting of corn in a very large geography.  With the calendar continuing to move closer to June every day and with the recent rally with soybean prices, many growers are beginning to ask if they should switch their corn acres to soybeans.  The answer to the question contains many parts and has many different variables.  One of those variables that are often included is planting date.  The later into May the calendar climbs the more anxious growers become about planting corn.  The fear growers have with planting corn in the latter half of May is often two fold.  The first concern is the fear of losing yield potential and the second fear is having “wet” corn at harvest.  Both questions are valid and worth looking into a little further.

Do corn growers lose yield potential the later corn is planted?

There are many facts and figures available about how much yield reduction a grower should expect on planting corn past the “ideal” date.  But recent history will tell that in 2011, corn planted into June had exceptional yield potential, so who is right?  The graph below represents 345 individual data points from 2010 through 2015 that compare planting date to plot average yield.

There are two major points to consider on the graph:

1.       Yields are all over the board when compared to planting date

2.       The trend line “looks” like the later you plant the higher the yields climb?  The answer lies in the world of statistics.  The R² value tells how relevant the correlation between planting date and yield has been over the past 6 years.  The closer the R² value is to 1 the stronger the correlation is, the R² value for this example is 0.0089, which means there is no correlation between planting date and final yield in AgriGold’s plots over the last six years.

What about planting corn early to maximize yield?

The message every winter at grower meetings is to plant early to maximize yield, so why has the message changed?  Simply the message has not changed, early planting date allows growers to maximize yield under ideal growing conditions.  Growers can maximize sunlight interception, rainfall and drydown windows if the timing of heat and rain are ideal.  The hope of every grower is that each year is going to be ideal, so we plan for ideal.  But what if conditions after planting are not ideal?  Then growers adapt and adjust and ultimately corn yields will represent the result of either the severity of the growing conditions or the generosity of the growing conditions.  Looking at the graph below it does indicate that if yields are going to be maximized then early planting should be the focus, but likewise planting early does not guarantee high yields.  What ultimately determines yield is what happens after the corn is planted.

What factors affect corn yields after planting?  Here are list of just a few:

1.       Timing and amount of rainfall

2.       Timing and amount of 90 + degree days

3.       Timing and accumulation of GDU’s – fast accumulation prior to tasseling and slower accumulation after tasseling leads to favorable yield potential.

4.       Weather conditions in September & October that affect drydown

What about drydown, the later into May corn is planted?

Using the same data, there is a stronger correlation (R2 of 0.2442) that later corn is “wetter” at harvest.  While the “wetness” is going to vary from year to year and hybrid to hybrid, knowing the corn will carry a little more moisture can affect our hybrid choices.

Switching to an earlier maturing hybrid to gain more drydown is not always the best approach.  As maturities begin getting shorter so does the yield potential.  Research conducted by Purdue University and The Ohio State University demonstrated that corn shortens it’s GDU requirements by an average of 1.6 GDU’s per day to reach flowering and 6.8 GDU’s to reach black layer after it’s optimal planting date in early May.  The corn plant shortens its vegetative state by shortening the amount of heat it requires to reach tasseling.  Therefore, by knowing this, planting a 110 day hybrid on May 1^st will require approximately 2750 GDU’s to black layer and if it is planted on May 25^th will only require 2614 GDU’s to black layer.  This response allows growers to plant fuller season hybrids to maintain the yield potential without experiencing excessively wet corn at harvest.

Late Planting Considerations:

1.       If planning on a preplant anhydrous application consider delaying that until sidedress timeframe so as not to delay planting timing any longer than necessary.

2.       Consider how to reduce the amount of trips or aggressiveness of any tillage operations.  Any tillage done late into the seasons should focus on weed management and leveling of seed bed only.  Consider using an herbicide burndown and no-till where applicable.

3.       Planting populations do not need to be decreased, but can be reduced up to 5% due to warmer soils and faster emergence.

4.       Switching to earlier hybrids – Until the 1^st of June most hybrids can be planted without fear of not finishing before a frost.  The only hybrids that should be considered to be switched would be hybrids that tend to be on the full season end of a growers comfort level.  The switch should not be to a drastically shorter season hybrid due to their lack of adaptation and yield potential.

5.       As corn planting grows nearer to June 1^st, consider using hybrids that provide protection from European corn borer (VT2PRIB, VT3PRIB and STXRIB).  Later planted corn is an attractive option for moths to lay their eggs and yield losses of 20+ bushels can be exhibited in conventional corn versus traited corn.

Summary

Planting date is one of the factors growers can use to maximize yield potential under ideal growing conditions.  Under less than ideal growing conditions, timing of pollination, timing of heat or lack of heat and timing and amount of rainfall in comparison to planting date make a much larger impact on yield.  Therefore planting corn into late May does not inherently mean reduced yield potential.  By following sound agronomic practices later planted corn maintains the ability to produce profitable bushels for growers.

Source:  Purdue University. https://extension.entm.purdue.edu/pestcrop/2016/Issue4/

Once the corn has been planted and is ready to start emerging the final piece of the uniformity equation is to evaluate the uniformity of emergence.  By spending the time to evaluate your emergence success, a grower has two very useful pieces of information.  First, it provides vital information on how successful the uniformity of emergence was.  If the emergence was good, a grower knows they had their system fine-tuned, if it was not adequate, a grower can begin working their way backwards to identify where the system could be improved for next year.  The second piece of information is that within a couple weeks after planting a grower has a really good idea which fields has the maximum potential and can reallocate resources accordingly.  Fields that emerge within the 24-48 hour window have a higher % yield potential than a field that took 48-96+ hours to emerge.  The tighter the emergence window the more uniform the plants and ultimately the more uniform the ears will be.  If a grower is trying to determine if extra nitrogen needs applied, if fungicides will be profitable or if they would like to try a foliar fertilizer product to maximize production, the grower automatically knows the fields with the most uniform emergence should be the fields that are targeted with extra production dollars.

How do you accurately measure the emergence timing of a corn field?  The most accurate method is the flag test.  The flag test was designed and refined by the National Corn Growers Contest Winner Randy Dowdy.  Mr. Dowdy is a strong believer on the importance of uniform emergence and wanted an accurate and reliable method to quantify his emergence.  Here is how Randy performs the flag test:

1.        At approximately 85 GDU’s after planting, start checking for any signs of seedling emergence.  A light movement of soil may be necessary to identify those seedlings just below the soil surface.

2.       Mark off 1/1000^th of an acre, as this is the area you will quantify the emergence for the entire field.  Ensure the area is a representation of the majority of the field, either by soil type, topography or planting conditions.

3.       Once the first seedling can be seen (while you are on your hands and knees!) put a colored flag next to all the plants that are spiked through.

4.       Come back 12 hours later and place a different colored flag next to all the plants that have spiked since the last check.

5.       Check every 12 hours using a different colored flag each time, until all the plants within the 1/1000^th of acre are emerged.

6.       Make sure you record the order of flag colors and at what hour they were used.

The fields with the least amount of colors are the fields with the best uniform start and should carry a high % yield potential for that field. 

To verify if emergence does in fact matter on yield, take time to go to the field before harvest and collect all the ears from each colored flag into a bucket, weigh the bucket and learn which bucket has the most weight per ear.  The flag test and resulting yield check is a great learning tool to demonstrate how emergence can positively or negatively affect corn yields.

The first step in corn stand uniformity is getting the corn planter maintained and adjusted to plant the corn crop as uniformly as possible, the next step in the uniformity equation is achieving uniform emergence.

Germination is simply the process that allows a seed to sprout or begin to grow.  Although the definition is simple the actual process is quite complex.  The germination of a corn seed requires soil moisture to “reawaken” the seed and adequate temperatures to speed along the enzymes and chemical reactions that allow the cells in the corn plant to grow and reproduce. 

Corn growers know the importance of germination but often don’t believe they have much of a roll in that process.  Growers tend to be disconnected from the germination process because they cannot control the rainfall, sunshine and/or temperatures.  But, in all accounts where and how a grower places the corn seed greatly dictates the ultimate success and/or failure of germination.  The success of germination is achieved by providing the corn seed with adequate and uniform moisture, adequate and uniform soil temperature and adequate and uniform soil-to-seed contact.

Please pay close attention to the fact that no values are assigned to these requirements, the purpose for that is germination can occur at various temperatures and soil moisture conditions, but the grower’s goal is to achieve uniformity.  Research continues to show that once a corn seed spikes through the soil, all its neighbors need to spike through within a 48 hour window, to keep from becoming a weed.  Therefore if conditions are uniform (not necessarily perfect) the chance of having a uniform germination and ultimately uniform emergence is greatly improved.

How do the three requirements impact the germination process?

Adequate and Uniform Moisture in the Seed Zone: Corn kernels must absorb water equaling about 30% of their weight before germination can begin.  Therefore there must be enough water present in the soil.  Too little water stalls the process while too much water can lead to premature death by rotting.  Uniformity of soil moisture is necessary so all seeds have the same access to water.  Adequate soil moisture begins with uniform planting depths greater than 1 ½” to avoid uneven soil moistures caused mainly by tillage patterns through the field.  The other consideration with moisture absorption is the temperature of the water that is absorbed.  A majority of the water is absorbed into to the corn seed within the first 36 hours.  If the first “drink” of water is extremely cold, it causes the seed to go into shock and disrupts the emergence process.  Therefore to aid in uniform emergence ensure the soil water that the seed is absorbing is above the 50⁰ F level.

Adequate and Uniform Soil Temperature in the Seed Zone:  Adequate soil temperature is defined as being greater than 50ºF at the 2-inch depth.  Soil temperatures need to be above 50ºF for corn to germinate uniformly and quickly.  Any temperature below 50ºF will slow the process and cause germination to be variable resulting in loss of yield.  Once again a planting depth greater than 1 ½” may lead to lower soil temperatures compared to shallower planting, but the temps will be more uniform, which is the goal.  Potential causes for variability in soil temperatures in the seed zone include different soil types, uneven residue distribution and most often are caused by uneven planting depth.

Adequate and Uniform Soil-to-Seed Contact:  In order for kernels to absorb moisture quickly and uniformly, the soil must be firmly packed around the kernel.  Anytime there is an air pocket around the seed, moisture uptake is slowed and ultimately the germination process is severely hampered. To achieve adequate soil-to-seed contact ensure the double disk openers create a “V” shaped trench, the closing wheels system is centered over the row and there is adequate down force to gently pack the soil around the seed.  Obstacles to adequate soil-to-seed contact include cloddy fields caused by working soils too wet, open planting furrows caused by planting in soils too wet or by too much residue being present in the planter furrow.

Uniform germination leads to uniform emergence that leads to uniform plants and ultimately high yield potential.  When looking at the success of the planting operation and the germination appears to be less than desired, begin looking at the three fundamentals of germination to determine what can be fixed for future success.

Year in and Year out, uniformity is the key to consistently high yields in all growing environments.  Having uniformly spaced plants with uniform emergence and uniform ear size allows the corn crop to maximize whatever the growing environment provides them.  Fortunately uniformity can be managed by a grower.  The manageable world of uniformity in a corn crop encompasses three major areas, the corn planter, the germination environment and finally evaluation of the uniformity of emergence.  The next three articles will dig a little deeper into each of these areas to help provide some insight into how a grower can help their corn crop be more uniform.

The purpose of a corn planter is to singulate seeds and put them into the soil so that they can grow.  While this appears to be an over simplification of what a corn planter does, it allows a grower to understand how they can manage their corn planter to maximize their yields.  Any corn planter can accomplish the task, but not any corn planter can do it effectively and in a manner that is going to add yield and not subtract yield.  A well maintained and serviced corn planter with an operator who is paying attention to detail is the only one that is able to plant the seed in a uniform manner, into a uniform environment to produce a uniform crop.

The task of getting a corn planter ready to plant can be tedious and painful.  Checking all the wear parts on each row and ensuring everything is in good working order and then taking apart and rebuilding those units that need repaired can take a lot of time and patience.  Fortunately, all that work is not a waste of time.  A corn planter is a machine that takes a lot of maintenance to keep it operating at a high level of accuracy.  While getting the corn planter ready, growers need to focus on all the parts that are responsible for a corn planter singulating and placing the seed into the soil, these parts will either aid or hinder the corn crops chance of being uniform.

The process of checking the planter can be simplified by starting at the first piece of the puzzle and working from there.  The first pieces of the puzzle are the double disk openers.  There are several aspects of the blades that need checked.  The width of the blade needs to be greater than 14.5” in diameter.  The amount of disk blade that touches each other needs to be 1.5”-2” and all bearings need to be smooth and in good working order.

The second part of the equation is the seed meter.  All seed meters need maintenance and calibration to ensure that they are consistently singulating every seed.  Take time to take apart your meter and check for worn or damaged pieces and get them calibrated to the specific seed size and weight of the corn that will be planted this year.

The third part of the planter that should be inspected surrounds the seed tube and seed tube protector.  Ensure the seed tube is clear of any blockages and the bottom edges are not worn with sharp edges.  Check the wear on the seed tube protector so it is still wider than the seed tube, should be wider than 5/8”.

The next part is the seed firmer.  Even though the seed firmer is optional it is highly recommended for uniform emergence.  The seed firmer is designed to gently push the seed into the bottom of the seed trench to aid in uniform placement.  The seed firmers are made out of plastic and do wear out.  Ensure there is a minimum of 1# of down pressure on each firmer and that they are not showing any wear that would hinder their job performance.

The gauge wheels are the fifth element that need adjusted and monitored.  The rocker arms wear and should be checked to ensure the gauge wheels won’t travel too far up and down and therefore cause the planter to place the seed at un-uniform depths.  Ensure the gauge wheels are touching the double disk openers when they are in the up position, if they are too close or too far away, adjust by adding or removing spacers.  Spin them to ensure the bearings are in good condition and the wheels are in good condition.

The final piece of equipment on the corn planter to affect the seed is the closing wheels.  Closing wheels should be aligned over the middle of the row and bearings checked to ensure they will complete their job and that they have adequate down pressure to provide the final “tuck.”

If a uniform corn crop is the goal, one must start at the beginning of the process and that is the corn planter.  Focusing on the parts of the corn planter that are responsible for the precise placement of the corn seed will provide the most return for hours of work.  Once the planter is ready to plant a uniform corn crop, the next step is to understand how to work towards uniform germination.

 In many parts of the Corn Belt, corn tassels are emerged or will shortly be emerging.  Once tassels and silks are fully exposed this represents R1.  Once pollination is complete and little blisters start filling on the ear, the plant is in R2 growth stage.  The corn plant is converting from vegetative growth with massive nutrient up take to build the factory, to reproductive stages in which the factory will convert sunlight to photosynthates, and pack as much sugars as possible into the kernels.  Stresses during the reproductive stages can result in kernel set reduction, small kernels sizes, low test weight and reduced stalk quality issues. 

Fungicide application should begin when the flag leaf is exposed, with some studies showing positive results applying up to brown silk.  Most product of choice includes a curative and preventative active ingredients for best control of current disease pressure and for what could arise over the next several weeks.  Fungicide products do not improve or add yield, they are designed to protect the established yield from yield reducing stresses.  There are two ways to look at fungicide application Yield Protection and Plant Health.  The plant health side of the equation can become invaluable with a healthier and stronger stalk going into harvest.  

How to make the decision:

1.      Does this field still have Top End yield potential for the season

2.      Does this field have good stand counts and potential ear counts

3.      Does this field have a lot of residue

a.      Just because its C/SB rotation doesn’t mean you won’t find disease pressures

4.      Does this field currently have disease, that is currently spreading

a.      Gray Leaf Spot

b.      Northern Corn Leaf Blight

c.      Anthracnose

5.      Will stalk quality issues cause problems during harvest

6.      Is weather trending positive for disease pressure for the rest of season

Image 2 was from 2014 harvest.  This field did not have any Gray Leaf Spot (GLS) pressure at R1 Tassel emergence.  However, at harvest pressure was observed.

Image 3 had black Sharpe hashtags placed on both side of the GLS lesion.  This was done to determine what the pressure was like over time.  The lesion region that is past the black hashtags represents how aggressive the disease has moved over time.  This is a great tool to track pressure and understand how aggressive the pressure is on a given hybrid or field.

Image 4 is a summary of several years’ worth of fungicide trials and the frequency of achieving a certain level of yield response.  This is a tool that can help making application decision. 

Recent heavy and persistent rainfall events have caused many soils to become saturated and even some to the point of flooding.  With the 10 day forecast continuing to show significant chances of rain in many areas, nitrogen management is becoming extremely important.  Numerous acres have all of their nitrogen applied and are sitting with saturated soils, while the remainder has limited to no nitrogen applied.  Each of these scenarios presents some opportunities as well as challenges to ensure the corn crop has adequate nitrogen to finish the crop.  Here are some practical steps to help make some decisions:

Step #1 – Assessing yield potential:

Assessing yield potential is extremely difficult and totally subjective, but experience and some basic information can lead to a better decision.  When a grower is faced with saturated to ponded soils during the early stages of corn growth and development, nitrogen is not the limiting factor.  Oxygen is the actual limiting factor at this stage.  Corn roots are a respiring organ and thus “breathe” oxygen to survive.  When the soil is saturated with water, all the oxygen has been forced out of the pore spaces and none is available for the plant roots, this can occur within 48 hours of the soil being saturated.  Once oxygen is depleted, the corn plant is living on borrowed time.  Most agree that corn can survive around 4 days of ponded water with relatively cool temperatures and less as the temperatures climb above 80°. 

When corn plants are subjected to oxygen stress during ear development, the plant will lessen the number of kernels each plant will produce to compensate for the less than ideal growing conditions.  But, even though once a corn plant has aborted kernels, there is no way to regain them, all hope is not lost.  There is still a lot of time to make each kernel bigger and drive yield through kernel size instead of kernel numbers.

Below are some arbitrary numbers that represent real life scenarios that have been experienced under extended saturated soils.  The numbers are only to help a grower decide how much yield potential their particular field may still have.  This information allows more reliable decisions will be made.

Corn fields showing no symptoms of water damage, but have had prolonged saturated soils may not have a significant yield loss, but may be limited at the end of grain fill due to the loss of nitrogen.

Step #2 – Understanding the different fates on nitrogen sources.

Nitrate Nitrogen or NO₃^- has a negative charge and since the soil also has a negative charge, the two repel each other and nitrate N is very mobile in the soil solution.  The majority of N loss is associated with the nitrate form.

Ammonium or NH₄⁺ is a very stable for of N.  It has a positive charge and it therefore attaches to the soil.  Ammonium N will be converted to Nitrate N in the soil, and the speed of that process depends mainly on the soil temperature.

Step #3 – Determining amount of nitrogen that is in the Nitrate form:

To determine the amount of nitrogen that has been converted to nitrate nitrogen multiple the total units of nitrogen applied by the percentage that best fits your nitrogen source and timing from the graph above.

Step#4 – Estimating how much of the applied nitrogen has potentially been lost:

First determine how many units of nitrogen that have been applied are in the nitrate form from step #3.  Then multiply the amount of nitrate nitrogen by the % nitrate loss in the adjacent graph.

Example:  160 Units applied 3 weeks ago using UAN (28%) and the soils have been saturated for 5 days:

160 Units x 60% Converted to Nitrate = 96 units of nitrate nitrogen

96 Units of nitrate nitrogen x 75% loss = 72 units lost

Meaning with 160 units applied – 72 units lost = 88 Units left to grow the corn crop.

Step# 5 – How to adjust nitrogen program to maximize performance:

When the growing season gets challenging and the corn crop is looking tough, growers tend to want to give up on the crop.  But, when nitrogen is the limiting yield factor, there is some amazing hope.  Two studies completed by Purdue University demonstrated that corn can recover from significant nitrogen deficiencies all the way to V15:

·        2010 study demonstrated that a V15 application of nitrogen yielded 100 bushels more than the starter only control and yielded only 13 bushel less than the V7 application of the same amount of nitrogen.

·        2007 study showed a 64 bushel advantage when the nitrogen was applied at V13 versus the starter only control and yielded 18 bushel less than the V3 sidedress application.

Late application guidelines and strategies:

·        Plan on providing at least 1 pound of nitrogen per expected bushel of corn with the combination of residual nitrogen plus any rescue treatments.

·        As a general rule, if the soil are saturated and considerable nitrogen has potentially been lost the across the board recommendation is to add an additional of 30-50 units.

·        When using UAN (28%) drops are a must.  Any UAN that is applied to the corn foliage will be burned and if a significant amount of the plant is burned there is a proportional yield loss associated with it.

·        When applying urea broadcast, 100-125# of product will provide the least amount of foliage burn, higher rates will increase burn and could harm yields.  The addition of ammonium sulfate in a broadcast application is also beneficial for its stability and ability to provide some much needed sulfur.

·        The use of controlled released urea is not recommended in a rescue situation due to the delay between application and the release of the nitrogen to the corn crop.

·        In a nitrogen rescue situation where yields have been lowered due to water damage, the addition of any stabilizers and/or Urease Inhibitors may not provide any economic returns and the cost/benefits should be weighed before using them.

The take home message is not to give up on a corn crop, but to ensure that everything is being done to help it maximize and to provide the highest return possible.

Recent heavy and persistent rainfall events have caused many soils to become saturated and even some to the point of flooding.  With the 10 day forecast continuing to show significant chances of rain in many areas, nitrogen management is becoming extremely important.  Numerous acres have all of their nitrogen applied and are sitting with saturated soils, while the remainder has limited to no nitrogen applied.  Each of these scenarios presents some opportunities as well as challenges to ensure the corn crop has adequate nitrogen to finish the crop.  Here are some practical steps to help make some decisions:

Step #1 – Assessing yield potential:

Assessing yield potential is extremely difficult and totally subjective, but experience and some basic information can lead to a better decision.  When a grower is faced with saturated to ponded soils during the early stages of corn growth and development, nitrogen is not the limiting factor.  Oxygen is the actual limiting factor at this stage.  Corn roots are a respiring organ and thus “breathe” oxygen to survive.  When the soil is saturated with water, all the oxygen has been forced out of the pore spaces and none is available for the plant roots, this can occur within 48 hours of the soil being saturated.  Once oxygen is depleted, the corn plant is living on borrowed time.  Most agree that corn can survive around 4 days of ponded water with relatively cool temperatures and less as the temperatures climb above 80°. 

When corn plants are subjected to oxygen stress during ear development, the plant will lessen the number of kernels each plant will produce to compensate for the less than ideal growing conditions.  But, even though once a corn plant has aborted kernels, there is no way to regain them, all hope is not lost.  There is still a lot of time to make each kernel bigger and drive yield through kernel size instead of kernel numbers.

Below are some arbitrary numbers that represent real life scenarios that have been experienced under extended saturated soils.  The numbers are only to help a grower decide how much yield potential their particular field may still have.  This information allows more reliable decisions will be made.

Corn fields showing no symptoms of water damage, but have had prolonged saturated soils may not have a significant yield loss, but may be limited at the end of grain fill due to the loss of nitrogen.

Step #2 – Understanding the different fates on nitrogen sources.

Nitrate Nitrogen or NO₃^- has a negative charge and since the soil also has a negative charge, the two repel each other and nitrate N is very mobile in the soil solution.  The majority of N loss is associated with the nitrate form.

Ammonium or NH₄⁺ is a very stable for of N.  It has a positive charge and it therefore attaches to the soil.  Ammonium N will be converted to Nitrate N in the soil, and the speed of that process depends mainly on the soil temperature.

Step #3 – Determining amount of nitrogen that is in the Nitrate form:

To determine the amount of nitrogen that has been converted to nitrate nitrogen multiple the total units of nitrogen applied by the percentage that best fits your nitrogen source and timing from the graph above.

Step#4 – Estimating how much of the applied nitrogen has potentially been lost:

First determine how many units of nitrogen that have been applied are in the nitrate form from step #3.  Then multiply the amount of nitrate nitrogen by the % nitrate loss in the adjacent graph.

Example:  160 Units applied 3 weeks ago using UAN (28%) and the soils have been saturated for 5 days:

160 Units x 60% Converted to Nitrate = 96 units of nitrate nitrogen

96 Units of nitrate nitrogen x 75% loss = 72 units lost

Meaning with 160 units applied – 72 units lost = 88 Units left to grow the corn crop.

Step# 5 – How to adjust nitrogen program to maximize performance:

When the growing season gets challenging and the corn crop is looking tough, growers tend to want to give up on the crop.  But, when nitrogen is the limiting yield factor, there is some amazing hope.  Two studies completed by Purdue University demonstrated that corn can recover from significant nitrogen deficiencies all the way to V15:

·        2010 study demonstrated that a V15 application of nitrogen yielded 100 bushels more than the starter only control and yielded only 13 bushel less than the V7 application of the same amount of nitrogen.

·        2007 study showed a 64 bushel advantage when the nitrogen was applied at V13 versus the starter only control and yielded 18 bushel less than the V3 sidedress application.

Late application guidelines and strategies:

·        Plan on providing at least 1 pound of nitrogen per expected bushel of corn with the combination of residual nitrogen plus any rescue treatments.

·        As a general rule, if the soil are saturated and considerable nitrogen has potentially been lost the across the board recommendation is to add an additional of 30-50 units.

·        When using UAN (28%) drops are a must.  Any UAN that is applied to the corn foliage will be burned and if a significant amount of the plant is burned there is a proportional yield loss associated with it.

·        When applying urea broadcast, 100-125# of product will provide the least amount of foliage burn, higher rates will increase burn and could harm yields.  The addition of ammonium sulfate in a broadcast application is also beneficial for its stability and ability to provide some much needed sulfur.

·        The use of controlled released urea is not recommended in a rescue situation due to the delay between application and the release of the nitrogen to the corn crop.

·        In a nitrogen rescue situation where yields have been lowered due to water damage, the addition of any stabilizers and/or Urease Inhibitors may not provide any economic returns and the cost/benefits should be weighed before using them.

The take home message is not to give up on a corn crop, but to ensure that everything is being done to help it maximize and to provide the highest return possible.

Twisted whorls in corn can be referred to as Rapid Growth Syndrome.  This phenomenon occurs when leaves fail to unfurl properly and become tightly wrapped and twisted.  Growers typically begin seeing twisted whorls at V5 to V6 corn.  The lower most leaves are normal with the sixth or seventh leaf tightly wrapped, as if the rolled leaf has lost its elasticity.  Young leaves inside the whorl continues to grow but are unable to emerge through the wrapped upper leaves.  This continued growth creates pressure which causes the whorl to bend or kink at right angles to the ground.

The cause is typically due to an abrupt transition from slow growing conditions (cool, cloudy days) to rapid development (warm, sunny conditions) which we certainly have had in the last few days.  Some herbicides -cell growth inhibitors or growth regulators- can cause twisted whorls in corn and is often blamed for these symptoms.  However, rapid growth syndrome has occurred over the years in many fields where neither class of herbicide was used.  Instances of twisted whorls will vary by hybrid due to individual growth characteristics.

In most cases these whorls will eventually open up and growth will resume normally with no yield loss expected.  As these wrapped leaves open up, yellow leaves will become apparent across the field.  A few days of sunshine will green them up and the problem will no longer be visible, except for a few crinkled leaf edges left behind caused by their restricted expansion inside the twisted whorl.

Reference:  http://www.agry.purdue.edu/ext/corn/news/timeless/TwistedWhorls.html

Many growers in the Central Corn Belt are finding that their once dark green cornfields have now transitioned into a sea of yellow and lime green colors.  It seems as though this transition has happened overnight in some areas.  This situation occurs almost every year, but in some years, it becomes more noticeable.  The plants most generally recover, but there are various causes of this color change.

The Ugly Corn Stage

Color changes in the crop seem to suddenly appear around the V3-V5 (3-5 collars) growth stage when the crop previously looked healthy.  Upon emergence, the corn plant primarily grows off of food reserves stored inside the kernel.  These food reserves become less available as the crop matures and develops its nodal root system.  Once the plant gets to the V3-V4 growth stage the crop starts switching from growing off of kernel reserves and becomes dependent upon its nodal root system for water and nutrient uptake.  This can sometimes be a rocky transition because any injury or restriction that has occurred to the root system or poor growing conditions in general, will now start affecting the plant due to the lack of root mass and uptake.  A plant with a small root system cannot support its above ground vegetative tissue and deficiencies are expressed.  This timeframe is sometimes called “The Ugly Corn Stage”.  The crop can fully recover, but it will first have to grow a greater root system so it can reach out and capture the water and nutrients it is lacking.  Starter applications such as 2x2, pop-up, and shallow broadcast applications of UAN help this transition by positioning nutrients in closer proximity to these struggling root systems. 

Causes of Yellow Corn:

-Residue within the root zone – Corn on Corn, No-Till, heavy soybean residue conditions

-Compaction - wheel tracks and sidewall smearing

-Cool Temperatures

-Wet soils, poor drainage

-Herbicide could be a culprit, can contribute to other stresses

-Sulfur/zinc deficiency symptoms due to slow mineralization of OM, soil type differences

-Nitrogen tied up with residue

A week of dry, warmer conditions should get the crop to turn around as rapid root growth occurs.

Corn planting is upon us and many growers are still applying anhydrous ammonia to fields as their main nitrogen (N) source for the crop.  When planting closely follows an application of anhydrous ammonia, there is a potential risk of corn seed and seedling injury from free ammonia in the soil.  This will lead to the often asked question, "How long do I have to wait to plant corn after an ammonia application?"   The answer is not black and white and depends on several interacting factors listed below.

-       Time between ammonia application and planting

-       Ammonia application depth                

-       N rate

-       Soil moisture

-       Soil texture                                                                     

-       Direction of nitrogen application compare to corn rows

-       Distance between knives

Understanding Ammonia Movement in the Soil

When anhydrous ammonia is applied to the soil, it can disperse approximately 3 to 4 inches away from the injection point.   Most of this dispersal takes place within the first 24 hours. This means that a dispersion zone of ammonia, 6-8 inches in diameter, may exist every 30 inches, or whatever the knife spacing may be.   If this zone comes in contact with the seed or seedling roots, significant injury can occur.  Some factors that affect the travel distance away from the injection point include soil moisture, N rate and the tillage practices used after application. Since anhydrous ammonia has such great affinity for moisture, the wetter the soil, the less distance ammonia will travel. The drier the soil means it may travel further in search of moisture. Therefore, we typically see larger dispersion zones in coarser soils due to the lower water-holding capacity.  Obviously, the higher the N rate, the more concentrated the application band from injection point.

The figure below illustrates a typical ammonia dispersion zone and how application depth can result in this zone interfering with seed germination and/or seedling growth.  At an ammonia application depth of 6 inches or less and a 2 inch seed depth, the ammonia dispersion zone can intersect the 2 inch seed placement and can cause injury.  By maintaining an ammonia application depth of 7-10 inches, the ammonia dispersion zone should remain below the seed planting depth minimizing any potential injury.     

University Research on Planting after Ammonia Application

The rule of thumb is to wait one week after applying ammonia to plant corn.  However, under adverse conditions (dry soils, shallow application depths, high N rates, etc.), injury has been observed when ammonia was applied 2 or more weeks prior to planting.  In the table below, a University of Illinois study shows the effect of nitrogen rate, application depth and time between ammonia application and planting had on corn stands.  Obviously, the depth of application and time delay in planting was important in providing a safety zone between the ammonia dispersion area and the seed. 

Key Strategies for Minimizing Anhydrous Injury in Corn

·         There is no magic number of days to delay planting after ammonia applications.  The longer the waiting period the better. A good rule of thumb for planting time is 7-14 days after application.

·         Depth of ammonia application should reach 7-10 inches deep.

·         Tillage after application certainly stirs anhydrous ammonia up within the soil and makes it much less concentrated and less harmful to the small seed or seedling.

·         Avoid spring applications in strip tillage systems.

·         Apply ammonia at an angle to the corn rows to minimize contact of seed with ammonia zones.

·         Potential for injury is greater in dry conditions and coarse textured soils. 

·         Avoid applying high N rates in late spring applications.

·         Insure that the soil closes behind the knife openings to limit N loss and upward movement of ammonia toward the seed.

  Diagnosing Ammonia Injury in Corn

·         Browning of the roots.  Burnt radicle and nodal root tips.  Roots may turn black all the way to the seed in severe cases.  Stubby-looking roots.

·         Uneven emergence, slow growth of some plants and wilting of plants in dry weather due to reduce water uptake

·         Consistent wave pattern across the field where ammonia band crosses the corn rows

The “Art of Planting Corn” Series started out discussing how growing corn was more of an art and not really a science.  While there is a lot of science involved in the agronomy portion of raising corn, the actually implementation of that science is quite the art form.  The second part of the series focuses on the “art” of planting corn in April.  After many years of observations and walking fields there continues to be 2 fundamental differences of planting corn in April versus May.  Thus the “art” of planting corn in April is different than the “art” of planting corn in May.

Some would say that planting corn is planting corn and when you do it makes no difference.  But, experience and witnessing many, many different scenarios leads this seed agronomist to a different answer.  Remember planting corn is an art form and not a science so not everything works every time, but the odds are in our favor if we have two different mindsets to planting corn.  The two different mindsets all surround the notion that April planted corn is far more forgiving than May planted corn.  What is meant by forgiving?  We can tolerate lower populations, more compaction and more stress when corn is planted in April than May. So if April planted corn can tolerate more stress what are the 2 fundamental differences?  The first fundamental surrounds the soil conditions when planting and the second fundamental is concerned with the future weather, not the current weather.

Step one:  Mud corn in April, but not in May.  Remember planting corn is an art and to appreciate art we have to be open to new ideas and this is the foundation of planting corn in April.  Growers have been told, shown and begged not to plant corn when the soils are damp for many years by many different people.  The reason for the advice was simple that planting corn in damp soils causes sidewall and horizontal compaction layers. This is true, it does.  So why then would one suggest growers to do it then?  The other part of the story that is not told is that soil moisture is the grower’s best friend when dealing with compaction.  Moist to wet soils allow corn roots to easily penetrate compaction layers.  Therefore the idea is that any compaction layer that is created in April, there will be ample moisture available to get the corn roots growing down and through the compaction zones before the soils dry out and not limiting any yield potential.

If you can mud corn in April, why not May?  The odds say that there will be a good amount of rain after corn is planted in April and the soils will stay at least moist.  May does not hold those odds, and it is very likely that the soils will dry out and the compaction layers will harden off and the corn plant is stuck in a mess that limits yield.

Step two:  Plant at the beginning of warming trend, not at the end.  A typically grower will wait until the air temperature and soil temperature are both in their favor before planting corn.  For May planted corn that is the exact model to employ, while April planted corn that could spell disappointment.  The weather in April can be sporadic and there can be some crazy weather swings at times so this part of the art form needs to be included in the overall strategy.  The last time replant happened, what was the planting date compared to the weather event that caused the poor stands?  Typically it is 24-48 hours prior to the weather event.  Corn planted 48+ hours before the weather events have a much, much higher success rate.  Why?  Because they have had a chance to germinate and get established before unfavorable weather arrives.

To remedy the detrimental weather events, growers need to start earlier in the cycle than they are comfortable.  When looking at a seven to ten day forecast and it shows a warming trend, growers need to start on the beginning of that trend not at the end.  Soil temperatures are not important in April, but getting the seed in the ground early is.  By planting on the early side of the trend, the seed is able to get started and established before the next down turn in the weather.

Finally, does this art form really work?  How many times have you witnessed your neighbor planting corn in April and you have shaken your head wondering what are they doing?  You are waiting for the soil to be right before you start and that crazy person is “mudding” in their corn.  Then how many times is that the best looking corn field in the neighborhood and the local talk at harvest is 10-15 bushel better than yours?  Unfortunately this has happened to just about everyone, so maybe that crazy person isn’t crazy after all.  Maybe their artistic form is capitalizing on a few tricks that allow his art to be started earlier than thought before! 

Growing corn is far more of an art than a science. Why? Science is repeatable and explainable. There is very little in a corn field that is repeatable or explainable. For example one year a certain fertilizer program provides huge results and the next 3 years it yields nothing, for no explainable reason. Trying to predict the correct amount of nitrogen to apply is definitely an art and not a science. Another part of art is that every artist (corn growers) produces their “art” (corn) their own unique way. For instance different artists produce corn by using different planting populations, some do tillage, some do not, some use fungicides, everyone uses slightly different herbicide programs, etc. Science does not allow for such variations to be included in their formulas. Also artists prefer different colors for their canvases, some use green, some red, some blue and some even yellow!

One of the components of the “art” is planting date. There is no cut and dried answer as to when is the best time to plant corn is, but the best artist’s play the odds as what will give them the most consistent results and that is planting corn in April. By planting corn in April, growers provide their corn crop a larger window to build more grain. Planting in April allows corn plants to pollinate and begin grain fill before the dog days of summer hit. Grain tends to be drier, earlier with April planted corn, also test weights tend to be higher when compared to later plantings.

If April is a good time to plant corn, why don’t we do it every year? The answer is planting corn is an “art” not a science and one of the attributes to the “art” is the weather. Just like art, the weather is open to interpretation. Some rejoice when it rains, while others find no beauty in April showers. Ultimately the question for today is, will the attributes of the art of weather favor planting corn in April?

AgriGold has recently been introduced to a weather service called Weather Trends 360. Weather Trends 360 provides an 11 month forecast that they claim is 84% accurate. They use a totally different set of criteria than the traditional forecast models to create a long term weather forecast. Below is their forecast for Dayton, Ohio for the Month of April.

If the trends are accurate, Ohio should expect a warmer April with some potential windows for planting. More details on Weather Trends 360 can be found on their website: www.weathertrends360.com.

If the ‘art” of growing corn favors April planting and the “art” of weather is favorable to corn growers will you be ready to capitalize on this opportunity? Try circling a date in April, as the day you will start planting corn and keep that date for a target goal to have everything ready to plant corn. My date is April 17th, what is yours?

Many foresaw the harvest of 2014 being slow along with the drawn-out grain fill period and cool summer temperatures.  However, the calendar shows we’re now into the middle of October and several corn fields have been left untouched (along with several soybean fields, too).  Other than the wet weather, another potential factor is the current corn commodity price around $3.00 (or lower).  The biggest concern with leaving the corn dry down in the field is corn standability.

According to the USDA as of October 19, corn harvest for Ohio was at 23%, 9% behind the five-year average of 32%.  Also current and long-term weather forecasts don’t show any prolonged warm period where corn would be able to dry down.  Warm, dry conditions accelerate drying and cool, wet conditions slow drying. 

Hybrid characteristics affect field dry down.  Hybrids vary in how they dry down in the field after maturity.  During good weather conditions, grain dry down rates are relatively similar between hybrids.  However, when weather conditions are not conducive for rapid dry down, hybrid characteristics become important to determine rate of grain drying.  These would include kernel pericarp thickness, size and density of kernel, husk leaf number and thickness, husk coverage of the ear, tightness of husk and time of ear drop after maturity.

The other hybrid characteristic that needs attention is stalk strength and standability.  It has been reported in recent newsletters that stalk rots have been appearing throughout the cornbelt.  One unfortunate happenstance when corn is near record output is the strain on corn plants from large sinks (ears).  In many places the plant has cannibalized itself in order to fill the ear and this has created the perfect avenue for stalk rots to infect.  Please check your fields and isolate particular fields and/or hybrids that need harvested early.

It’s unsure if we’ll receive the necessary Indian summer to help the corn dry down or if we’ll see a bump in the commodity prices.  However, the corn has been made and the decision needs to be made of let the corn dry down in the field and risk the potential of stalk lodging or harvest the field.  If you have any questions or concerns about certain hybrids to target for timely harvest, please contact your local AgriGold Corn Specialist or myself.  I hope you continue to have a safe and productive harvest.

There are two topics you are told not to discuss, politics and religion.  But there are two topics most corn growers will discuss some time throughout the year, yield and test weight.  Both provide for lively debates and provide many different avenues for arguing way or the other.  But in every good “discussion” there needs to be a small bit of truth or fact to really stand firm.  Facts on yield are easy, pounds of grain per acre = yield, while the facts on test weight seem to be a little fuzzier at times.  The following article will hopefully shed a few truths in the next test weight “discussion” at the coffee shop.

Simply what is test weight?

Test weight is simply a volumetric measurement.  An official bushel measures 1.2445 cubic feet or 32 quarts.  Test weight is simply the weight of that volume.  Typically test weight is measured in a one quart container and then multiplied by 32 to obtain the actual test weight of the bushel.  Historically a bushel is a measurement of volume, not weight, but because of the limitations of selling on volume, it was decided that each bushel of corn weighs 56 pounds.  Therefore today corn is sold in 56 pound “blocks” called a bushel. 

Why does test weight differ between years, fields and/or hybrids?

There are many factors that influence test weight:  grain moisture, physical characteristics of the kernel, plant stresses and hybrid differences to name a few.  Depending on the year and growing conditions some or all can impact test weight at harvest.

Grain moisture:  Grain moisture is probably the largest factor that influences test weight.  As the grain moisture decreases, grain test weight increases.  Why?  There are two reasons:  The first is as corn dries it also shrinks, thus allowing more kernels to fit into the quart measurement container.  Second, as the corn dries the corn naturally becomes more slick (seen in how “wet” corn stacks higher in wagons than “dry” corn) which allows for better packing.

Determining exactly how much test weight increase there will be when dried is variable.  Individual hybrids react differently to drying, the overall condition of the grain as lower quality will gain less than higher quality.  Also, the speed and heat that is used can affect the gain of test weight.  Grain that is dried at temperatures higher than 180 degrees will have less of an increase due to “cooking” of the grain.  But for a general rule of thumb, refer to the graph to the right.

Physical characteristic: The physical characteristics of individual kernels play a huge role in determining test weight.  Essentially how well do the kernels pack together in the measuring bucket.  The kernels size, density, shape and “slickness” of the outer kernel impact the pack ability and ultimately the test weight.

Plant Stresses:  Plant stresses are a major factor in determining the final test weight.  Plant stress is defined as anything that keeps or slows the movement of water and nutrients to the kernel during the grain fill period or causes the kernel to be damaged (ear rots & molds).  The stresses can include leaf or stalk disease, low fall temperatures, insect damage, poor fertility or poor nutrient uptake, drought, hail and premature frost.

Hybrid differences:  Each genetic family carries different test weight characteristics and can greatly influence the final test weight. 

What is test weight an indication of?

Grain quality:  Test weight is a general indicator of grain quality.  The higher the test weight for a given hybrid genetics normally means higher grain quality.  For example hybrid A’s normal test weight is 55 pounds, if it  carries a 57 pound test weight it generally means it is of higher quality than if it was 54 pounds.  Test weights do decrease as grain deteriorates.

Grain storability:  Test weight tends to be a good indicator of corn storability.  Corn that is below 54 pounds per acre should not be stored into warm weather and dried below 15% moisture.  Also softer corn can be more easily damaged during handling.

Is there any correlation to test weight and yield?

Often high test weight is associated with high yields and low test weight with low yields.  “Your corn would have yielded more if the test weight was higher,” is a familiar tune that very seldom rings true.  According to Mike Rankin, Crop & Soils Agent for University of Wisconsin Extension, “In fact, there is a poor relationship between test weight and yield.  The same test weight can exists across a wide range of yield environments and genetics.  Similarly, there can be a wide range of test weight values across the same high or low yielding environments.”

Are growers selling test weight or pounds per acre?

There is a difference as to what is being measured.  Test weight measures the weight of a “volume” bushel of corn which is equivalent to 32 quarts.  But growers are paid on the “weight” bushel that is based in units of pounds.  The “weight” bushel of corn is exactly 56 pounds.  Therefore in the following example a grower hauled in 85,000 pounds of 54# test weight corn and another grower hauled in 85,000 pounds of 59# test weight, each grower got paid for 1,517.9 bushel.

“Cost” of low test weight corn….

The following example demonstrates how test weight figures into what a grower is paid at an elevator for differing test weight levels.

While the economic factors of test weight are negligible, there is another factor to test weight not discussed to this point and that is the volume piece of the puzzle.  The heavier the test weight the more pounds that can be transported and stored in the same size container as compared to lighter test weight corn.  The volume line in the above graph demonstrates that point.

Summary:

Corn yield is simply the number of pounds or corn harvested in a certain area, while test weight is the measure of how many pounds of corn can fit into a certain volume.  Test weight is only partially related to kernel weight, other factors such as grain moisture, hybrid genetics, the physical characteristics of the kernel and the level of plant stress during grain fill.

References:

Bern, Carl & Brumm, Thomas.  “Grain Test Weight Deception.”  Iowa State University Extension.  PMR 1005.  October 2009.

Hurburgh, Charles & Elmore, Roger.  “Corn Quality Issues in 2008 – Moisture and Test Weight.”  Integrated Crop Management News.  Iowa State University Extension.  October 2008.

Nafziger, Emerson.  “Test Weight & Yield: A Connection?”  University of Illinois Extension.  Crop Development Bulletin.  October 3, 2003.

Rankin, Mike.  “Understanding Corn Test Weight.”  Extenstion Team Grains.  University of Wisconsin.  October 2009.

Late fall planting, harsh winter conditions and/or excessive rainfall can all lead to an undesirable wheat stand in the spring.  Often growers would like to turn those failed wheat acres into a corn field and questions arise as to how to best ensure a successful transition.  Planting corn into a growing wheat crop that has failed requires some planning and several key management considerations to establish and grow a high yielding corn crop.  Those management considerations include one, killing the existing wheat stand to avoid the competition of early season weeds.  Two, nutrient management and the intricacies associated with the existing nutrients and future nutrient recommendations.  Third, identifying tools and keys to ensure a successful stand establishment is obtained.  Fourth, insect pressure is greater in volunteer wheat stands and need to be controlled to ensure a prosperous corn crop. 

The first step is to kill the remaining wheat crop prior to planting the corn.  Corn is very sensitive to early season competition and killing the growing wheat will eliminate that competition.  The most effective method to kill the wheat crop is through the use of herbicides.  The two best options include a glyphosate (1.5# a.i./A) + 2,4-D (1-2 pts/A) program and a Gramaxone (3-4 pt/A) + atrazine (1.5# a.i./A) + 2,4-D (1-2 pts/A)program.  The Gramaxone based option is more expensive but does provide a faster burndown for immediate planting.  Also when growers will be trying to kill a wheat stand the temperatures could be colder and the Gramaxone based system is less sensitive to cooler temperatures than the glyphosate program. 

When using an herbicide program to kill the wheat stand, the best timing simply is the earlier the better.  By killing the stand earlier less moisture is lost from the seedbed; the decomposition process is sped up and will reduce the negative effects of allelopathic (Allelopathy is the biological process where plants produce chemicals that influence growth, survival and reproduction of other plants) substances found in the decaying wheat.  The second option to kill a stand of wheat is by tillage.  With tillage come several obstacles, moist soil conditions and the “chemical” effect on the young corn plant.  When most wheat fields need tilled the soil conditions are often wet and will be difficult to work and create an ideal seed bed.  The second obstacle begins when the residue is worked into the soil.  The decaying residue begins to tie up all available nitrogen as microbes do their job.  Also as the residue decomposes it releases allelopathic substances that can slow the growth of young corn plants.  To best maximize the tillage pass, set tillage tool as shallow as possible and keep the soil profile firm to reduce moisture evaporation.

Nitrogen Management:                                                                                                                   

A portion of the nitrogen that was applied to the wheat crop will be available to the new corn crop.  The challenge is determining how much nitrogen actually remaining.  The amount that is remaining can vary depending on the source of nitrogen, the amount of rainfall the field has received and the recent temperatures.  Warm, wet weather with ponding occurring is a recipe for high nitrogen loss.  If the wheat crop is frost killed, a majority of the nitrogen will be available throughout season.

To determine the amount of nitrate nitrogen available to the growing corn crop, consider taking a Presidedress Soil Nitrate Test (PSNT).  A PSNT should be taken when corn is at the four to six leaf stage, just ahead of the sidedress application of nitrogen.  The PSNT is designed to estimate the amount of nitrate nitrogen that is available in the soil.  If the PSNT reports more than 25ppm nitrate nitrogen, no additional nitrogen is recommended.

When planting into a failed wheat crop, a majority of the soil nitrogen will initially be tied up by microorganisms that are breaking down the wheat residue.  To successfully balance the tie up of soil nitrogen and the young corn plants need for nitrogen, a starter with nitrogen is recommended or applying additional pre plant nitrogen via UAN solution will meet the early season corn crops nitrogen needs.

Insect Management:

Wheat is a grass crop just like corn and there is a potential for grass loving insects such as black cutworm, wireworm and armyworms to have a huge impact on the young corn crop.  As the wheat crop begins to die and decay the insects will move from the wheat to the corn and begin feeding on it.  The “greener” the wheat crop is at planting the more potential for insect damage in the corn.  The best options for insect control is one, wait until the wheat crop is brown before planting, which would be approximately 2 weeks after the herbicide application, or two, use an insecticide with the herbicide to stop or slow whatever insects are present.  Also consider using a seed treatment package that will provide protection for any wireworm infestations.

Herbicide Carryover:

Any herbicide applied to the wheat crop could pose a concern for carryover.  Some herbicides will not allow another crop to be planted that season, while others have a set interval of days between application and planting the next crop.  Refer to the label of any herbicides that were applied to the wheat crop to ensure there will be no herbicide concerns.  ALWAYS READ AND FOLLOW LABEL DIRECTIONS.

Summary:

When a wheat crop fails whether from water damage, loss of stand and/or freeze damage, planting a corn crop into the failed wheat stand is often a profitable adventure.  When planning how to best succeed there are some important steps AgriGold recommends a grower implements to improve their chances for success.  The first step is to chemically kill the wheat stand with either a glyphosate or Gramaxone herbicide program.  Leave the residue on top of the soil profile and no-till the corn into the field.  When planting ensure there is adequate starter nitrogen applied either with the planter or a pre plant application of an UAN source with the herbicide.  Also, include an insecticide labeled for control of black cutworm and armyworms with the herbicide application.  Use seed that is treated with a 500 rate or higher of seed treatments such as Poncho, to protect against an infestation of wireworms.  A few simple strategies can help ensure the challenges of planting corn into a failed wheat crop will be mitigated and a successful corn crop achieved.

Reference:

Johnson, Bill, Tony Vyn, Jim Camberato, Christian Krupke and RL (Bob) Nielsen.  Considerations for planting corn into damaged fields of wheat.   Purdue University.  Available at: http://www.agry.purdue.edu/ext/corn/news/articles.07/WheatCorn-0411.html (7/18/13)

Converting failed wheat acres to corn.  Available at: http://www.aganytime.com/Corn/Pages/Article.aspx?name=Converting-Failed-Wheat-Acres-to-Corn&fields=article&article=175 (7/18/13)

In a corn plants life, there are three distinct periods that influence the potential yield, vegetative growth, pollination and grain fill.  All three areas influence yield in different ways.  Vegetative growth determines the potential ear size, pollination is responsible for taking the potential to actual kernels to be filled and grain fill takes the fertilized ovule’s and turns them into plump full kernels of corn.

The ideal environment for grain fill includes sunny days with daytime temperatures in the mid-80s followed by nighttime temperatures in the 60’s complemented by timely rainfalls and a continual supply of nitrogen.  All these ingredients are necessary to grow high corn yields, each is important in their own way, but ultimately they work together, if one is missing or limited, all the other ingredients do not work as effectively.  Here is how these ingredients during grain fill are vital to a grower’s success:

Sunny days:  Photosynthesis is what makes all green plants run.  Photosynthesis takes the energy from the sun and uses it in combination with water and nutrients to provide energy for cells to live, produce sugars, amino acids and other building blocks for grain production.  The more sun energy the corn plant can intercept, the more building blocks the plant can produce and ultimately the more yield that can be made by each plant.
2013 Report Card:  Sunshine was at a premium in most corn fields during the grain fill period.  There were extended periods of time that were overcast or mostly cloudy.  All of the hours that were overcast limited the amount of photosynthesis a corn plant could perform.  The limited production limited the vital ingredients the corn plant needed to fill the high yield potential.  The stress associated with the loss of photosynthetic production can be seen in many fields with tip back and premature death.

Daytime temperatures in the mid-80s:  Heat is the driving force behind the maturation of the plant and kernels.  Corn plants are effectively driven by growing degree units (GDU).  The corn plant requires a certain number of GDU’s to complete its life cycle and the overall speed in which the plant acquires the necessary GDU’s determines the overall life span.  If temperatures are too hot, the plant will shut the system down and if it is too cool, the system will potentially want to run longer than it was designed.
 
2013 Report Card :  The entire state experienced a 5 to 6 week period during grain fill where daytime temperatures were well below normal.  The cool temperatures actually extended the potential grain fill period providing an opportunity for higher yields but it also caused the corn plant to work a significant amount of overtime and the extended grain fill period asked the corn plant to stay alive and healthy for an longer period of time, thus adding to the overall stress level of the corn plant.
Nighttime temperatures in the 60’s: Night time temperatures play a vital role in the success of grain fill.  When nighttime temperatures stay in or above 70, the corn plant spends all night wasting energy to keep cool.  Essentially the corn plant is not able to “rest.”  But, when the night time temperatures drop below 70, the corn plant is able to “rest” and redirect the energy it produced during the day into the kernel for higher grain production.
 
2013 Report Card:  The nighttime temperatures were about as ideal as can be expected during grain fill.  Most evenings were in the mid to lower 60’s allowing the corn plant to “rest” and allocate its resources toward grain fill instead of trying to keep cool.

Timely rainfall:  Water performs two important roles in grain production.  The first role is to transport nutrients throughout the plants along with keeping plant cells functioning.  The second role is to transport nutrients from the soil into the corn plant.  When water is readily available the corn plant is able to easily move the necessary nutrients into and throughout the corn plant while keeping the plant cells active. 
 
2013 Report Card:  Late July through September the amount of rainfall combined with the soil moisture level did not fully meet the corn plants water requirements causing the corn plant to allocate it’s resources and limit the amount or resources available for kernel fill and development.  The lack of rainfall not only directly impacted the corn plant but it indirectly caused nitrogen to become limited in the soil profile.

Continual supply of nitrogen:  Corn plants need a continual supply of nitrogen to grow big yields.  Nitrogen is the nutrient that allows the corn plant to grow robustly and fill the kernels to their maximum.  The key to any nitrogen program is to ensure there is enough present long enough to build maximum yield.  Although the strategy seems simple, nitrogen has many enemies in the field; excessive rainfalls, ponding water, dry weather and time.  

2013 Report Card:  Keeping a continual supply of nitrogen available to the corn plant was very challenging in 2013.  Many corn fields experienced significant amounts of rainfall early in the growing season that lead to ponding and saturated soils.  Many of these fields experienced moderate to high nitrogen loss.  The second challenge came when the rain stopped.   Nitrogen requires water to move through the soil and into the corn plant and when the soil profile dried out, nitrogen stopped moving.  Unfortunately the dryness was during the peak of grain fill.  When nitrogen is limiting the corn plant has to adjust.  The first adjustment is to begin pulling nitrogen out of its reserves, the lower leaves.  As the amount of time nitrogen is limited increases, more and more leaves will be sacrificed until the level of nitrogen in the corn plant is too low, then it must begin aborting kernels to ensure grain fill success in the older kernels.

What happens when one or more ingredients is missing?  Think of the corn plant as two individual units, the plant and the ear.  The ear is what receives all the plants produced “energy” and it requires the same amount of “energy” everyday no matter what and the bigger the ear, the more “energy” it will need.  The plant is responsible for producing that “energy.”  Normally the system works well and the plant is able to meet all the “energy” needs without a problem.  The issue arises when one or more of the ingredients are missing.  The missing ingredients cause the plant to lower its production of “energy” and it must either lower the amount of kernels it is trying to fill by aborting kernels from the tip and/or begin tapping its reserves in the stalks and roots.  If the plant is unable to meet the ears “energy” requirements for an extended period of time, the plant will ultimately die prematurely.  Corn plants that have high yield potential and spend any amount of time missing one or more key ingredients will show sign of premature death first, compared to lower yielding fields.
Although not everywhere has there been missing ingredients during grain fill or if there were they were not missing long and high yields can be expected.  But there were also areas where some ingredients were missing for a considerable amount of time.

The goal before harvest is to critically evaluate the corn production system and ask if the system was fully ready to take advantage of the high yield potentials given to growers in 2013.  Even if the “cream” is gone due to circumstances outside of our control, being able to ensure all the controllable factors were managed for high yields is a producer’s goal.  If some controllable factors can be improved upon, now is when needed adjustments can be made.

Corn is planted, sprayed and nitrogen has been applied and with the current weather trend it is growing very rapidly.  So what can growers expect and plan for next in their corn fields?  The next major stage for the corn plant is the switching of priorities from growing the vegetative portions of the corn plant to the reproductive stage.  The switch happens with a big bang and a lot of fanfare that corn growers call tasseling.  When the yellow tassels shoot out from the plant it is announcing that a fundamental change is occurring.  The change is that all the corn plants resources are now going to be used to produce only grain.  From planting to tasseling, corn growers have worked hard to ensure the corn plant developed the largest ear possible and after tasseling the corn grower has to sit back and watch the ear develop and grow.
 
One of the biggest factors in determining yield is how big and healthy the corn factory is.  The corn factory is the roots, stalks and leaves of a corn plant, they all work together to collect water and nutrients to build the sugars and carbohydrates that drive high yields.  The other job of the corn factory is to collect as much sunlight as possible.  Sunlight is the energy source that drives the factory and the factory is more productive the more light it can intercept.  Light interception is the main responsibility of the corn leaves.  Corn leaves are the finest example of solar panels, collecting and utilizing every ray of light it can intercept.

The corn leaves ability to intercept large amount of sunlight depends on how much healthy leaf area is available.  The biggest threat to the functionality of the leaf area is leaf diseases such as gray leaf spot, northern corn leaf blight, common and southern rust and/or anthracnose leaf blight.  Leaf diseases do not directly affect the corn plant but indirectly it reduces the leaf area that can be used for photosynthesis.  Less leaf area typically equates to lower yield potential.
 
To help determine if the corn crop is at a significant risk of a disease infestation there are three areas of concern, weather conditions, inoculum level and hybrid susceptibility.  Weather conditions that favor leaf diseases include rainy/humid conditions and without rainy conditions, cloudy weather with extended dew periods can also increase the potential for a severe infection.  The inoculum level is increased as more residue is present on the soil surface.  The residue is where most of the leaf diseases overwinter and the more that is present the more potential for a high infestation.  Third, the susceptibility of the host corn plant is the final piece of the puzzle.

Hybrid susceptibility can be broken into three categories, susceptible, intermediate and resistant.  University researchers have taken these three different susceptibilities and created some recommendations for foliar fungicide applications.  Susceptible hybrids should be sprayed when disease symptoms are present on the third leaf below the ear on 50% of the plants.  Intermediate hybrids have the same guidelines as susceptible hybrids with the addition that the field has a history of a foliar disease problem such as the previous crop is corn, there is 35% or more residue left on the soil surface and the weather is warm and moist.  Finally the resistant hybrids generally do not respond to foliar fungicide applications and it is not recommended to spray these hybrids.  To determine a hybrids level of resistance consult with your local seed representative.
 
Once corn plants begin to tassel it is no longer able to maintain the strong defenses it has during the vegetative growth.  If leaf diseases are present prior to tasseling, they will flourish and continue to reduce the amount of leaf area available for photosynthesis.  If there are little to no signs of leaf diseases by brown silk, the chance for yield loss due to a late infestation of leaf diseases is minimal.  But if the corn plant is under attack prior to brown silk and action is not taken, the window of opportunity is lost.

Corn plants are growing fast and the leaf diseases are hidden under the canopy of the corn crop therefore a trip into the field is necessary to determine if the corn factory is under attack.  By scouting corn fields several days prior to tasseling growers will have time to determine if a foliar fungicide application is necessary.

The 2013 corn crop is officially planted and growing.  If growers were asked in April how successful they were going to be in planting corn the outlook would have look dim.  April was cool and damp and the prospects of an early planting season quickly went out the door.  But, May arrived and for a great majority of the State, a large planting window arrived.  Corn was planted very quickly with almost 67% of the crop planted in only 14 days.  With the corn crop planted and a majority of nitrogen has been applied, let’s take a look at where the corn crop is compared to past years.
Ohio’s Planting Progress:
 
Planting progress started considerably slower than in 2012 and the 5 year average.  Very little corn was planted in April throughout Ohio.  Starting the first week of May, many areas started planting corn.  As the days went by, more and more growers started planting corn.  Planting did not stop for any considerable length of time and was completed in a timely fashion.  The only portion of the State that kept planting from being completed earlier was in extreme Southwest Ohio, where every rain event hit and hit big and planting was delayed until the Memorial Day weekend.
Ohio Growing Degree Update:
Corn development is closely related to heat, therefore the more heat that is accumulated the faster a corn plant will grow.  The best way to measure this heat accumulation is by using the daily high and low temperatures to calculate growing degree units (GDU).  With the GDU system is calculated by subtracting 50 from the average daily temperature.  The average daily temperature is determined by adding the daily high temperature to the daily low temperature and dividing by 2.
 
The growing degree unit (GDU) accumulation for Ohio is right on the 5 year average.  By being on the 5 year average of GDU accumulation the corn crop is on pace and growing at a steady pace.
Corn Crop Growth Update:
Corn plants need a certain amount of growing degree units (GDU) to complete different growth stages.  For instance a corn plant needs 125 GDUs to emerge.  Also from V1 (1st leaf collar) to V10 (10 Leaf collars) leaves emerge at a rate of 1 leaf per 85 GDUs and from V10 to final stage emerge at a rate of 1 leaf per 50 GDUs.  Knowing how many GDUs that have accumulated since emergence growers can estimate the current growth stage and predict future growth stages.
 
The Ohio corn crop is off to a good start and stands are as good as they were planted.  With normal rainfall and normal GDU accumulation, the Ohio corn crop stands a great chance to be at or above yield line trend.

The continuous march of weather systems across the Corn Belt has delayed planting in many areas. As a result, some growers are considering switching full season hybrids to earlier maturities. Bob Nielsen, Purdue Extension Corn Specialist, says, "The reason why we worry about delayed planting corn, of course, is not so much the yield losses associated with delayed planting, but more so the ultimate question of whether a corn hybrid will even mature before a killing fall frost."
 
Nielsen and Peter Thompson, The Ohio State University Agronomist, concluded a four-year study on the effects of delayed planting on the Growing Degree-Day (GDD) needs of corn. They found that a typical corn hybrid's GDD requirements to reach physiological maturity decrease about 6.8 GDDs per day of delayed planting after May 1, meaning corn planting that is delayed by 30 days would need 210 less GDDs. A hybrid rated at 2800 GDDs with normal planting dates in late April, would require only 2596 GDDs to reach maturity when planted at the end of May. Table 1 outlines several common AgriGold hybrids and how later planting dates influence the overall GDDs required to reach physiological maturity, or black layer. GDDs for Table 1 are calculated from the time of planting. Understanding that early season GDD accumulation is slow compared to summer and early fall and the fact that full season hybrids will reduce their GDD requirement to reach maturity, growers should not panic if considering switching maturities.

Optimum planting date studies indicate that corn planted May 15th will produce 95% of optimum yield while corn planted May 20th will produce 91% of optimum yield. However, yield potential will most likely be greater with a fuller season product versus an early maturity corn less adapted to the area. Full-season hybrids can give a yield advantage, but they also may result in high-moisture grain at harvest due to late planting. Therefore, growers should consider drydown and grain quality of particular hybrids if they are thinking of switching due to weather delays. Switching to earlier maturity hybrids not adapted to a specific area may be just as risky as planting full season products due to limited disease and heat stress tolerance. Should planting delays continue, Table 2 outlines the average GDDs that are accumulated between various planting dates and the average first fall frost date for different locations. To use this table effectively, consult Table 1 to determine how many GDDs are required for a hybrid to reach black layer, and then cross reference Table 2 to determine how many GDDs will accumulate for that specific planting date and location. For example, if a grower in Springfield, Illinois would plant A6533 on May 25th, Table 1 indicates that 2727 GDDs are required for physiological maturity. Table 2 then indicates that on average, 2963 GDDs accumulate in between May 25th and October 14th for Springfield, Illinois. For this situation A6533 should be "safe" from an average fall frost. This table is based upon averages and should be used as a reference only.

Keep in mind that planting date is only one factor that determines the yield of a corn crop. Timely rains and moderate temperatures in July and August can have a considerable impact on corn yields and may be more important than planting date as was the case in 2008 and 2009. "In fact," Nielsen says, "If you compare statewide average corn yields with the date by which 50 percent of the state's corn crop was planted, you will find little relationship between delayed planting and corn grain yield."
 
Here are some delayed planting tips:
• Do NOT take chances and switch to early-maturing hybrids not adapted for your area.
• There is no need to change the seeding rate. If anything, seeding rates can be declined by 5% to compensate for better germination and stand establishment in warmer soils.
• A seeding depth of 1.75 to 2 inches is generally a good depth, with deeper seeding to reach uniform soil moisture, if necessary. The soil tends to dry out faster later in the season, and shallower plantings can equate to uneven emergence.
• If anhydrous ammonia has not been applied yet, delay nitrogen application until after planting. Reduce nitrogen amounts to the level of the expected yield.

Sources:
 
Nielsen, R.L. (Bob) and Thompson, Peter. "Delayed Planting & Hybrid Maturity Decisions." Agronomy Guide - Purdue University Cooperative Extension Service. 2003. Purdue University/The Ohio State University. 29-4-2013. <http://www.agry.purdue.edu/ext/pubs/AY-312-W.pdf>
 
Angel, Jim. "Illinois Frost Dates and Growing Season." Illinois State Water Survey. 2010. University of Illinois at Urbana-Champaign. 4-5-2-2013. <http://www.isws.illinois.edu/atmos/statecli/Frost/frost.htm>
 
Guinan, Pat. "When Can We Expect Our First Autumn Frost in Missouri?" Missouri Climate Center. 2009. University of Missouri at Columbia. 5-5-2013. <http://climate.missouri.edu/news/arc/sep2009.php>
 
The Weather Chanel. "Growing Degree Days Calculator." 4-5-2013. http://www.weather.com/outdoors/agriculture/growing-degree-days

The first day of corn planting is always an exciting time of year.  Anticipation is running high, nerves on edge and sometimes patience is a little lacking to give that planter a final look over.  The importance of that final look over could simply mean the difference between success and failure!  With over 12 attempts to plant a perfect crop while being at AgriGold, I have been provided some unique opportunities to explore those not so perfect attempts.  With lessons learned and experience gained, all of it is worthless unless shared with others; therefore I wanted to pass along the most important last minute thoughts.

Before heading to the field one final check of the corn planter is invaluable.  Using the marks in the gravel 3 key functions of the corn planter can be quickly checked and fixed if necessary.

A. Fertilizer row unit spacing & operation:  If the planter is equipped with starter fertilizer units, a quick measurement can be made on how far the fertilizer unit is located from the row unit.  Then if adjustments need made they can be accomplished quickly and the measurement can be rechecked prior to heading to the field. 
The first two objections I have heard concerning checking the starter fertilizer unit placement is: 1. “I’ve planted with the planter for 5 years and they’ve been okay for 5 years” and 2.  “I just got the planter and the previous owner used it, so they are okay. “ The trouble with these statements is that the spacing may have never been correct and if the fertilizer is placed too close under the right environment, the seed will be burned and killed.  Secondly the units may have moved due to a loose bolt or jarring during previous planting trips.  20 minutes spent double checking fertilizer placement can save hours of stress later in the season when it is too late to do anything about it.

Also by running fertilizer through the pump and down through the fertilizer coulters while the planter is being driven on the gravel allows for easy recognition if all the parts of the liquid fertilizer units are functional.

B. Closing wheel system alignment:  One of the most unadjusted parts of the planter is the closing wheels.  Growers simply assume the closing wheel systems will be centered over the row, but with many years of walking behind planters the closing wheels are often off centered and therefore not properly “tucking” the corn seed gently into the seed trench.  A simple visual inspection will confirm if any closing wheels will need adjusted.

C. Seed drop:  By checking the seed drop prior to hitting the field, a grower can quickly check to ensure all row units are planting and the entire system is operational without spending a lot of time digging for the seeds in the field.

2. Check tire pressures:  Planters sit more than they move and the down time can lead to some air loss.  The planter is designed to operate with the proper size tire and at the correct psi.  Any variation from the manufactures recommendations can lead to a planter either over applying or under applying seed.  Double check the planter’s manual to determine the correct pressure and check each tire to ensure proper inflation. 

Also correct tire pressure is important for equal weight distribution along the planter.  A tire that is low will cause the weight of the planter to be shifted to other tires which could lead to more compaction in those areas.  Low tire pressure can also lead to more weight being carried on each row unit leading to more down pressure and ultimately more sidewall compaction issues.

3. Check fertilizer and planting sprockets:  Take a few minutes to double check with the manual to ensure both the fertilizer and planting population sprockets are set according to your plans in 2013.

4. Three must do’s when the planter is pulled into the field for the first time:
a. Level the planter:  Planter levelness is very important to the entire planting operation.  If the planter is running nose down, it will cause the coulters to cut deeper than the double disk openers causing the seed to be placed at different depths.  If the planter is running nose up there is more pressure placed on the back half of the row unit leading to more sidewall compaction.   Take a moment to examine the main frame of the corn planter once it has been placed in the ground and pulled forward several hundred feet.  If it is not level make appropriate changes.

b. Check the planting depth on each row:  No matter the make, model or number of rows, each unit has its own personality.  Checking the planting depth on only one or two rows only ensures those one or two rows are at the correct depth.  Each row should be checked and set individually to maintain the uniformity of planting depth that is critical to uniform emergence.  The process of checking every row is time consuming but could reap huge rewards if there are several rows planting significantly deeper or shallower.

c. Walk behind the planter as it is planting:  The final step to ensuring the best planter pass possible is following behind the planter as it is planting through the field.  The tractor operator cannot see all the closing wheels, hear the sounds of the planter and witness first hand all that is happening at ground level.  By simply walking or driving an ATV behind the planter, someone can witness if all aspects of the planter are operating properly.

When the sun is shining and the weather warms the bug to plant corn hits hard and fast.  Often the last minute checks and balances are left undone in the race to get corn planted.  By taking the time to check over the planter one last time, a grower will ensure that all the corn planted is done accurately and that the corn seed is given the best chance for the highest yield potential.

Recently the USDA released their 2012 county corn yield estimates. Being able to compare country performance to one another is always interesting and this communication serves to review and highlight how each county performed in recent years. The first map highlights the results from the 2012 corn cropping year. The second map shows the current 6-year corn yield average (2007-2012) and the third map demonstrates how many corn acres each county harvested in 2012.  For those growers who like actual numbers, included is a list with more detail actual county corn yields along with how other states in the Corn Belt performed in 2012.
 
These three maps, along with the raw data, should put the 2012 crop year in perspective. The information also sheds some light on how your county and surrounding areas have been performing in regards to corn production over time. All of this data was gleaned from the USDA/NASS web database.

Map 1 shows the extreme variance in corn yields throughout Ohio in 2012.  There were definitely areas that received timely rains while other portions of the State did not receive enough rain to wet the sidewalks.  Data is shown in Bu/Acre.

Map 2 demonstrates that even with a very a couple of challenging years, the overall yields that past 6 years in Ohio have been very respectable.  Data is shown in Bu/Acre.

Map 3 highlights the number of corn acres that were harvested in 2012 in each county.

The images to the right show raw Data for Corn Yield Data in Ohio from the past 6 Years.

The winter season is upon us. The list of things that needs done every winter seems to get bigger and bigger each year, from Christmas Gifts, Taxes, Seed orders, Fertilizer and Chemical Programs, and of course don't forget about the dreaded "Honey-Do List". With all of these things at the forefront of our minds we often forget about proper pH planning.
 
The pH management of our soil is one of the most important factors for crop production. However it always seems to be overshadowed by the management of the macro-nutrients, Nitrogen, Phosphorus, and Potassium. The reality of the situation is that an improper pH can play a major role in the availability of these nutrients. It also happens to be one of the more difficult nutrients to fix within the soil in a short time frame. That being said, the fields that need limed in the fall of 2013 need decided on right now.

Proper pH
 
Soil pH is a measure of soil acidity or the active hydrogen in the soil solution. A pH < 7.0 is acidic and a pH > 7.0 is alkaline. The ideal soil pH for corn and soybean production is 6.5 to 7.0. A pH of 7.0 is considered neutral. There are three main contributors to increased soil acidity in our crop fields, Rainfall, Nitrogen Fertilizers, and Legumes like Soybean and Alfalfa.
 
Soils that were formed under more rainfall will typically be more acidic than soils formed in more arid conditions. Water (H20) combines with Carbon Dioxide (CO2) to form Carbonic Acid. When the weak acid ionizes in the soil it releases a Hydrogen Ion (H+). The released H+ displaces a Calcium Ion (Ca++) causing the soil to become more acidic.
 
Nitrogen fertilizers that contain or are converted to Ammonium (NH4+) contribute to soil acidification. Products like Anhydrous Ammonia, Urea, and Ammonium Nitrate all go through the nitrification process which basically converts Ammonium to Nitrate(NO3-), which is the plants preferred form of nitrogen uptake. When this conversion takes place, Hydrogen Ions (H+) are released in the soil.
 
Crops such as Soybeans use more cations such as Potassium (K+) and Calcium (CA++). As they take in these cations, their roots excrete H+ ions to maintain an electrochemical balance within the plant tissue resulting in acidification.
 
Why Lime is used
 
The more acidic a field becomes the more nutrient tie up occurs resulting in lower yields. In order to correct soil acidification, Ag lime is applied to our soils. Ag lime is used because it contains Calcium Carbonate (CaCo3). The more pure calcium carbonate lime contains the more effective it is in correcting your soil pH. The chart below illustrates how an acidic soil can tie up fertilizers that are applied, and effect fertilizer efficiency.

Tips for Liming
 
Any successful lime program has a process. This process involves soil sampling, building proper lime recommendations, dispatching trucks and a good spreading job with calibrated equipment. Below are a few tips that will make your liming experience as efficient as possible.
 
1. Grid Sample - There are very few crop production fields in the Midwest that have no variations in them. Often times the amount of money you will save on the cost of lime after grid sampling will pay for the cost of the sampling. It's smarter to put 3 ton in some areas and 1 ton in others rather than blanket applying 2 tons per acre. The maps below show a central Missouri farm that was grid sampled the fall of 2011.

The map on the right shows the variations in pH from 5.4 to 7 and the map on the right shows the variation in lbs. of lime that would be applied from 0 to 3,000 lbs. per acre.
 
 
 
     2.     Start Planning Now - The process of liming takes much more time and preparation than fertilizing. The lime order has to pass through many different channels before it gets spread on the field. The Lime spreading company, Quarry, and Trucking company all have to be on the same page in order to cover a large amount of acres in one lime season. Try to lime fields that are coming out of corn and going to soybeans. Typically we harvest corn much earlier which results in a bigger window of opportunity to get lime piled and spread. Lime will tend to freeze in the beds of trucks once the temperature starts to dip below 32 degrees F. In general the drier the lime the longer you can haul in colder temperatures.
  
     3.     Not all Lime is Created Equal - Choose your lime wisely. Remember the more calcium carbonate lime contains the more effective it is on neutralizing your soil. Also, grade size can play a big part in the time it takes to raise the pH of soil. The finer the grade size, the quicker it will work. The quality of lime can differ greatly from one quarry to another. One of the best ways to find good lime is to check with the trucking companies that are hauling it. They often know which quarries have the biggest supply and best quality of lime.
 
References
Mosaic, Efficient Fertilizer Use Manual- pH, by Dr. Cliff Snyder
 

Corn Harvest has started in some parts of the State while other areas are only a few weeks away from starting.  With harvest so close, there is much anticipation about how good or how bad the corn crop will actually yield.  The 2012 growing season has had numerous challenges including lack of water, high temperatures, questionable pollination and a lack of late season heat, but unfortunately the growing season is not done providing growers with challenges.  The current challenge facing corn growers is the formation of ear rots in many corn fields.

Fusarium kernel rot is caused by several different species of Fusarium and is the most common fungal disease on corn ears.  The Fusarium pathogen overwinter very well on corn and grass residue and is more often seen in no-till, minimal-till and continuous corn fields.  The Fusarium fungus thrives in environments that are hot and dry after pollination.  The pathogen is also amplified by drought stress at silking.
 
Typically Fusarium kernel rot is found on scattered kernels or in small groups of kernels throughout the ear.  It is identified by whitish pink to lavender "fuzz" that covers the kernels.  Often only kernels that are damaged due to insect feeding or silk cutting are prone to a Fusarium infestation, but under ideal conditions undamaged kernels can be infected.  Ears that remain upright during heavy rainfall events and/ or have poor husk cover tend to be more susceptible to extensive rotting.
 
With ear rots being present, corn harvest and grain handling become very important.  The largest concern with Fusarium kernel rot is that it can produce a mycotoxin called Fumonisin.  Fumonisin is problematic and can cause pose a serious health risk to swine and horses.  The challenge surrounding Fusarium kernel rot is that mycotoxins levels in the grain do not correlate well to the amount of kernel rot present because not all strains of Fusarium produce mycotoxins.

Gibberella Ear Rot is recognized by a pink, red or deep red mold that develops from the ear tip and progresses towards the base of the ear.  Corn husks will often adhere tightly to the ear and a pink to red mold will grow between the husks and ears. The pathogen that causes Gibberella ear rot overwinters on infected crop residue. Both corn and small grain residue are carriers. Gibberella spreads from the crop residue unto the corn silks via splashing rain water and infects the corn ear. The disease is more severe when cool, wet weather occurs within the first 21 days after silking. The ear rot is more severe when water collects between the ear and the husk. A hybrid with a tight style husk is more susceptible to Gibberella ear rot than a loose husked hybrid. There are feeding concerns with Gibberella ear rot because it can produce mycotoxins. The most common trichothecenes produced in corn is deoxynivalenol (DON), also known as vomitoxin. Swine and other monogastric animals are the most sensitive species to vomitoxins. If there is concern, take a 10 pound sample and have it tested prior to feeding to livestock.

Diplodia ear rot is caused by the fungus Stenocarpella maydis.  Diplodia is identified by the thick white mold that starts at the base of the ear.  The white mold will ultimately change to a light gray color or brown over the husks and kernels.  One visual symptom of infection is the early appearance of a bleached or straw colored husk with raised black fruiting bodies late in the season if infection occurred early.
 
Corn is the only known host for this fungus.  The fungus overwinters on corn residue.  Due to this, corn on corn acres and reduced or no-till acres are at a greater risk of infection.  Infection by Diplodia is enhanced by dry weather prior to silking, followed by wet conditions at and just after silking. Ears are most susceptible to this disease during the first 21 days after silking. Insect damage generally associated with corn borer and corn ear worm may also allow for a point of entry and cause the damage to be accentuated.  Damage caused by diplodia reduces test weight and yield along with lower nutritional value of affected grain.  There is no known mycotoxin problems associated with diplodia ear rot and therefore no feeding restrictions. 

Aspergillus flavus can be identified as an olive green or yellowish green powdery fungus on drought stressed corn ears.  The fungi survive on plant residue and produces abundant spores.  These spores are then carried by wind to infect silks and damaged kernels.  Short husks that expose ear tips are more susceptible to kernel damage from insects and weather, therefore more prone to infection by Aspergillus.  
 
The major concern with Aspergillus is its ability to produce aflatoxins.  Aflatoxins are naturally occurring by-products produced by two types of molds: Aspergillus flavus and Aspergillus parasiticus. Aspergillus flavus is the most common and often found when corn is grown under stressful conditions such as drought.  Aflatoxins are harmful and can cause several problems in livestock, most commonly a reduction in feed efficiency and reproductivity, suppression of immune system, and in rare instances, death.  The most abundant aflatoxin, aflatoxin B1, is a carcinogen. This raises human health concerns because aflatoxin can appear in the milk of dairy cows fed contaminated corn.
 
Handling Grain for Fields with Ear Rot:
 
The proactive strategy to handle kernel rots is to harvest corn fields earlier than normal.  The general guideline is if 10% of the ears in the field have at least 25% of their kernels infected, early harvest is warranted.  Fusarium kernel rot will continue to grow on ears out in the field and will eventually cover the entire ear with a heavy cottony growth.  The ideal harvest moisture for fields with kernel rots is 25 - 27% moisture.  If a grower is going to store grain contaminated with kernel rots, they should dry the grain to below 15% as quickly as possible and then cool the grain to below 50 degrees soon after drying and try to store the grain in the bin below 30 degrees.

Estimating Corn Yields Prior to Harvest:
Harvest is quickly approaching, yes it may be hard to believe but harvest is not far away.  With the early planting and extended periods of heat, the corn crop is maturing rapidly.  There is really only one more major task in the corn field in August and that is estimating what yield the corn field will provide.
 
Estimating yields is an educated guess and is really only as good as the sample that is taken, but it does provide growers with a little window of what is to come.  By estimating yields growers can better secure their grain marketing strategy, determine if there is adequate bin space or simple prepare themselves for what harvest is likely to bring.
 
Estimating corn yields prior to harvest can be accomplished in several fashions, but the most widely used method to estimate the yield of a corn field is a rather simple equation:

The key to making the yield estimation formula work is by accurately sampling the field.  The standard procedure is to take yield estimates from 5 to 10 areas of a field and sampling 5 randomly selected ears from each of the sections and then average the results to gain an estimation as to what the corn field will yield.  Typically the yield estimation formula is accurate to within 20 – 30% plus or minus the actual yield.
 
As with any year, 2012 has presented a few unique challenges that are going to make estimating yield difficult is some fields.  Due to the challenges an explanation of what the challenges are and how we can work around them to gain the best yield estimate is necessary.
 
Challenges to Yield Estimating in 2012:
 
1.  Uneven pollination and ear size:  Corn planted in April had a difficult time emerging uniformly due to non-uniform soil moisture and cold soil temperatures  and the dry weather throughout the growing season has caused a great deal of exaggeration of that unevenness all the way through harvest.  Many corn fields appeared to have emerged evenly at the time, but as tasseling approached and pollination completed the unevenness in the corn fields are evident.  In every field planted in April there are many plants that are fully pollinated intermixed with corn plants that were still trying to pollinate a month later and simply missed the pollination window.  When estimating yields in fields with plants that are shorter and have a significantly smaller ear, the grower must not count those ears in his final ear count for the yield equation.  By taking out these runt plants a more accurate yield estimation will be completed.

2. Kernel depth:  The yield estimation equation assumes that all corn kernels are of same and therefore it can easily underestimate the yield of deep kernelled hybrids and overestimate the yield of shallow kernelled hybrids.  The 2012 growing season is shaping up to be a shallow kernelled year due to the lack luster and shortened kernel fill period for the corn planted in April (the jury is still out on kernel depth on May planted corn).  Therefore if a grower simply follows the yield estimation equation, the kernel count and population can lead to crazy high yield estimations that are unrealistic.  To better handle the variation in kernel depth a simple adjustment to the equation will help.  The equation assumes that it takes 90,000 kernels to make a bushel by volume, if the 90,000 is adjusted to 100,000 for shallow kernels and 85,000 for deep kernels the results will be more accurate and in line with the realities of the growing season.

Stalk Quality Issues
 
Numerous corn fields throughout the State are showing some kind of a nutrient deficiency, mainly nitrogen and potassium deficiency.  The deficiencies are a plant deficiency not a soil deficiency.  The reason for the plant deficiency is because most nutrients need water to be transported from the soil into the corn plant.  Without the water as a carrier the corn plant cannot acquire the needed nutrients from the soil and therefore must begin moving that nutrient from older parts of the plant to the ear. 
 
The other challenge facing many corn fields is a shallow root system.  With a shallow root system there is significantly less area for the corn plant to scavenger for nutrients and water.  The unfortunate combination of lack of water and shallow root systems the corn plants are experiencing a strong limitation in some key nutrients.  The challenge facing growers with limiting nitrogen and potassium to a corn plant is the fact both nutrients are important in maintaining stalk integrity and strength.  If a corn field is showing signs of a nutrient deficiency or has been under long periods of dry weather, keep a careful eye on the stalk integrity and be prepared to harvest early to minimize any stalk lodging issues.

Challenging Grain Fill Period:
 
The dry weather throughout the growing season has been the main topic at the local coffee shop and although it is important there is also another topic as important, the heat.  Heading into August, the state had experienced some extremely high temperatures.  The high temperatures not only caused great discomfort to those working outside, it also sped up the corn plants grain fill process.  Grain fill begins right after pollination and does not come to an end until black layer.  The amount of time between these two events largely depends on how fast the corn plant accumulates heat units.  Typically, the longer the grain fill period the higher the yield potential.  The higher yield potential is due to more time being allotted to the corn plant to produce starch and fill the kernel.  In contrast a short grain fill period tends to lead to lower yields due to less time to produce starch.  The 2012 grain fill period is estimated to be about 46 days for corn planted in April and about 50 days for corn planted in May.  For reference in 2011 Ohio had an estimated 64 days of grain fill and in 2009 there were 75+ days of grain fill, both years produced very high yield levels in corn across the state.
 
The final yields are not only determined by the length of the grain fill period as demonstrated in 2010 when there were an estimated 49 days of grain fill and the State average was 163 bushels.  There are often other factors that play into the final yield level.  The 2012 corn crop has had a few challenges during pollination and grain fill that will play a major factor in the final corn yields for each farm.  Below is a few of the challenges and the corresponding result:

The 2012 growing season will not be forgotten for many, many years to come and the challenges we have faced will leave a lasting impression on our farming decisions for years.  Therefore as harvest approaches there will be many growers pleasantly surprised at the yields they are receiving and there will be some who are disappointed with their yields, but in both cases the importance of trying to correlate what the corn field went through and when the stresses and/or rains arrived will greatly help explain what and why a grower is harvesting the yields they are harvesting.

Pollination is just beginning in some areas and a few weeks out in other areas.  With the forecasted heat and continued dry weather, growers pray that pollination shed and silk emergence timings coincide with minimal disturbance.  But once the pollen starts flying the real question for growers is has pollination been successful?  Shortly after fertilization, growers can walk through their corn fields and determine the success rate of pollination.  The following procedure can be used to determine the success rate of pollination.

Step 1:  Collect Ears.  Select several ears from different areas throughout the corn field.

Step 2:  Cut thru the husks with a knife.  Carefully cut down thru the corn husks, start at the top of the ear and cut down.  Be careful not to cut the silks or the cob in the process.

Step 3:  Open husks at the cut.  Once the husk has been cut, slowly open the husks around the area cut.  Pay attention not to disturb the silks. 

Step 4:  Pull the husk off the ear.  Start with the outside layer of husks and slowly remove each layer.  Once again be careful not to disturb any of the silks.

Step 5:  Gently shake the ear.  Once the husks are removed, gently shake the ear to allow loose silks to fall off the ear.

Step 6:  Examine the ear for remaining silks. Once a kernel is fertilized the silk detaches from that kernel.  Any silk that remains attached to the kernel has not been fertilized and depending on the amount of time left for pollination the kernel may or may not be pollinated.

Once complete, this method will provide a general idea of how the representative ears inspected have pollinated.  After pollination, there are many other factors (mainly weather) that will determine the harvestable yield.  Ears still have the option to abort kernels due to excessive heat, nutrient deficiency, disease, etc. to keep the ear intact.

The term “factory” best describes what the purpose of a corn plant is.   A factory is built to produce a specific product and a corn plant is built solely to produce grain.  Just like any successful factory, it must be built on a solid foundation.  The corn plant is no different; it must also have a solid foundation.  The foundation of a corn plant is its roots.
 

The current foundation of the corn crop is being stressed due to the unusually dry soils.  Typically, the best defense to dry conditions is a deep and expansive root system.  When corn roots live in a good rooting environment, they are able to grow deep and find much needed resources.  What makes 2012 challenging is that many of the corn fields have very poor rooting environments.  Numerous circumstances have caused those rooting challenges.
 
Tillage layers are being exaggerated due to dry soils.

Example how the soil will break apart where tillage tool ran and created a density change in the soil profile
 
Tillage layers are caused by running shovels or blades through soils that have excessive moisture. Often the soil surface appears ideal and dry at the time of soil preparation, but below the surface the tillage tool is causing a density change that can limit root growth. When soils stay moist, corn roots have enough strength to easily push through these layers, but when the soil turn off dry the density change becomes hard and almost impenetrable by the corn roots, thus keeping roots from being able to move deeper into the soil profile to acquire additional moisture. The best scouting tool to determine if a field is being hampered by a tillage layer is to dig up a corn plant and carefully allow the root ball to break apart. If there is a tillage layer, the ball will break apart easily with a flat area being exposed that the roots are not aggressively growing through.

Density layer caused by field cultivator operating in moist soils that the corn roots cannot penetrate
 

Sidewall Compaction is limiting root expansion:
 
Sidewall compaction is caused by the double disk openers smearing the side of the seed trench and then having too much down pressure that packs the soil tightly. Once again the soil surface may appear to be dry and in great condition, but at the planting depth, the soils can be just moist enough to be smeared and packed. The compacted sidewalls act as two concrete walls keeping the corn roots from expanding to their full potential. The only option the corn roots have is to grow straight down until they are free of the zone. The lack of horizontal growth greatly limits the area the roots can explore for nutrients and water. To diagnosis if the corn field has sidewall compaction, dig up a corn plant and before knocking off the soil, examine how the roots are growing, if they are growing with the seed trench only, then sidewall compaction is a limiting factor to root growth.

Roots that are trapped in the planting trench that have no option but grow straight down

Example of a soil that is smeared by the corn planter and how the corn roots cannot penetrate that "concrete" wall
 
Shallow planting has caused shallow rooting systems:

 Corn fields planted shallower than one inch are demonstrating a lot of variability and lack of strong vigor. When setting the planter depth, many growers are only concerned with how fast the corn emerges; they do not consider that planting depth also determines how deep the nodal (main) root system begins. Shallow planted corn inheritably has a shallower starting main rooting system. Under adequate soil moisture shallow planted corn may not be a problem, but under hot and dry soils the shallow planting is problematic. Roots cannot grow where there is no moisture, in dry soils shallow roots may even "burn" off, causing an even smaller root system. Dry soils and shallow planted corn leads to small and ineffective root systems that cannot thrive in stressful condition.

An example how shallow planting leads to uneven corn when moisture is limiting
 

Unfortunately there are no easy fixes to the current rooting challenges other than rainfall. The shallow and underdeveloped rooting systems will continue to present challenges the rest of the growing year. As the summer continues and growers begin to wonder how well the corn crop will do, take time to examine the foundation of the corn crop, if the foundation is solid, the chance of having a higher than expected yield is likely. But if the foundation is shallow and weak, the corn crop will struggle to deal with the stresses it will likely experience in 2012.

The spring of 2012 is shaping up to be another planting season to remember. Late March was warm and beautiful and got a lot of growers excited about planting corn, then April hit. The first portion of April was decent but after the 10th of April the temperatures were less than ideal. While the soil conditions were good in most areas the less than ideal soil temperatures kept most growers wondering when to plant corn. Unfortunately the cool to cold soil temperatures were in fact a major hindrance in corn growth.

Above ground symptoms of corn plants infected with seedling blights.
 
While most corn planted in Mid-April emerged, that emergence took two to four weeks and once it emerged, the growth has been less than ideal. The latest concern on the corn planted on April 17th thru April 20th is a large and often devastating infestation of seedling blights. Seedling blights is a generic term for soil-borne pathogens such as Pythium and Fusarium attacking the struggling corn plant. The major impact of seedling blights is the loss of corn stands.

Corn stand loss due to seedling blights depends on three factors: 1. The duration of time the soil remains saturated (not just flooded), 2. The growth stage of the corn. 3. The average soil temperature. Essentially all corn is susceptible to corn seedling blights simply because there is little to no resistance to soil-borne pathogens. The seed treatments, such as Acceleron provide approximately 10 to 20 days of protection. The only long term protection the corn plant has against seedling blights is rapid growth. The rapid growth allows the corn plant to outgrow the infection of pathogens. Unfortunately corn seedling diseases are most severe under cold, wet conditions. The ideal soil temperatures for seedling blights are 50-55º F. When temperatures are below 60º F, corn is not growing rapidly and is therefore highly susceptible to seedling blights.
 
"Mesocotyl" Below ground symptomology of a corn plant infected by seedling blights.
 
"Seedling blights may be either pre-emergence, in which the seed germinates but the seedling is killed before it emerges from the soil, or post-emergence, win which the seedling emerges through the soil surface before developing symptoms. With pre-emergence seedling blights, the coleoptile and developing root system then turn brown and have a wet, rotted appearance. With post-emergence seedling blights, the seedlings tend to yellow, wilt and die. Brown sunken lesions may be evident on the mesocotyl (region between the seed and the nodal root system). Eventually the mesocotyl becomes soft and water soaked. Mold growth may be evident on decayed seed or plant tissues. The root system is usually poorly developed and the roots are brown, water soaked and slough off." (Sweets, 2000)

With the high potential for seedling blights, field scouting is critical to adequately determine the health of a corn field. When scouting a corn field foseedling blights examine both the healthy and non-healthy looking plants for signs of brown spots or total death. The seedling relies on the seed for its main nutrient source until V3. After V3, the nodal roots provide the plant with the needed nutrients. Without a seed for nutrition the seedling cannot survive for very long. Therefore if the corn plant is taller than V3 and the mesocotyl is damaged there is a strong likelihood the plant will survive, while corn smaller than V3 will eventually die due to the seedling blights. Examining corn fields now could help eliminate any surprises later in the summer.

                                                                                                Above ground symptoms of corn plants infected with seedling blights
 
                                                                                                                                                                                                                                                                                           
 
Sweets, Laura; Wrather, Allen. "Integrated Pest Management, Corn Diseases." University of Missouri-Columbia Extension. 2000.

Each year many corn growers that use spring applied, preplant ammonia find some degree of anhydrous ammonia injury within their corn fields. Severe injury can cause significant germination problems or root pruning, which leads to stand loss or uneven stands, which can ultimately lead to significant yield losses.   As the spring of 2012 begins, much of the corn belt has found itself putting on a lot of ammonia and considering planting very soon. This means that the time between anhydrous ammonia applications and planting will most likely be very minimal in many cases. Injury from anhydrous ammonia can be easy to diagnose but somewhat difficult to prevent. Below are some precautions and preventative measures to take to avoid anhydrous injury in corn.
 
Movement in The Soil
 
The first step in preventing anhydrous ammonia injury in corn is to understand how anhydrous moves in the soil. When anhydrous ammonia is applied to the soil, it can disperse approximately 3 to 4 inches away from the injection point.   Most of this dispersal takes place within the first 24 hours. This means that a solid band of ammonia, 6-8 inches in diameter, may exist every 30 inches, or whatever the knife spacing may be.   This band can very harmful to a germinating seed or a seedling root system that is trying to establish. Some factors that affect the travel distance away from the injection point include, soil moisture, amount of N being applied, and the tillage practices used after application. Since anhydrous ammonia has such great affinity for moisture, the wetter the soil, the less distance ammonia will travel. The drier the soil, means it may travel further in search of moisture. Obviously, the more ammonia being applied the more concentrated the application band from injection point.
 
Diagnosing Injury in Corn
 
Generally, there are 3 signs that give the injury away. The first sign of anhydrous injury is a burnt radicle and burnt nodal root tips. The first root of a corn plant called the radicle should be 2-3 inches in length with many lateral roots extending outwards, resembling a "furry foxtail". (See Fig A) When exposed to high amounts of anhydrous ammonia, the tip of the radicle root is burnt, sometimes clear back to the seed in which it began. (See Fig B)

The second way to notice the injury is when the corn plants reach the rapid growth stage of approximately V5-V6. At this stage, plants that may have been injured by ammonia tend to get set back compared to other neighboring plants. The pattern resembles the same direction and pattern that the ammonia was applied, usually at an angle. This is due to heavy root burning just above the knife tracks or injection points, plants that were not injured away from the knife tracks go on to outgrow the other and pick up steam through the rapid growth stage, taking on a dark green color and getting much taller. (See Fig C)

 The third sign then, is when the field is observed from a perpendicular view and the same knife crossing the row pattern shows a consistent wave pattern that many times gets mistaken for a bad starter pump on the planter. (See Fig D)

Preventing Anhydrous Injury in Corn
 
1.   If at all possible, placement of anhydrous ammonia should reach 8-10 inches deep, particularly spring applications.
 2.   There is no magic number of days to delay planting after ammonia applications, the longer the waiting period the better. Although a good rule of thumb for planting time is 7-14 days after application.
 3.   Avoid spring applications in strip tillage systems. Try to make strips, plant and side dress.
 4.   Avoid spring applications in no till. Try to plant and side dress.
 5.   Tillage after application certainly stirs anhydrous ammonia up within the soil and makes it much less concentrated and less harmful to the small seed or seedling.
 6.   Be extremely cautious on coarse textured soils.
 

Special Notes: Many times during the heat of the season, getting the ammonia applied and planting corn run so close together. If time is of the essence and you are willing to take the risk, make sure application is deep. If N rates are 180#N plus, consider limiting the amount on N applied with ammonia to 150# of actual N, then making up the difference with surface applied liquid UAN (28% or 32%). This will lower the concentration of the injected band below the seed.

The Eastern Corn Belt is experiencing one of the warmest winters on record.  Temperatures have consistently been 5-10 degrees Fahrenheit above normal for most of the winter months, with some locations recording 60+ degree temperatures in the month of February.  The warm weather throughout the winter could lead to a lot of unwanted situations in 2012.  One of the unintended situations caused by warmer than normal temperatures is the potential for high infestations of winter annuals.

Winter annuals are unique in that they grow during the cool times of the year when other annual weeds become dormant. The life cycle of winter annuals begin anytime between late summer and early spring.  The newly sprouted weeds overwinter as small seedlings and then when the weather begins to warm in the spring they continue to grow, flower, put on seeds and then die.  Winter annuals typically grow close to the ground for protection against cold winter days.  The young plants are very cold hardy and often stay green late into fall and are often the first plants to grow in the spring.

Two main factors dictate the severity of a winter annual infestations.  The first factor is favorable conditions during the early to mid-fall time frame.  The favorable conditions would include cool weather with favorable moisture.  The second factor is a mild winter that allows for continued growth throughout the winter months.  The current winter has met and exceeded all the requirements for a heavy flush of winter annuals in 2012.

Winter annuals do not have a direct impact on corn production, but do have an indirect impact on growing corn in fields with moderate to high levels of winter annuals.  There are really three indirect ways winter annuals interfere with corn production:

1. Dense populations of winter annuals can form a “mat” in the field.   The mat can slow soil drying and warming which in turn interferes with planting and tillage applications in the spring.  Most growers that have attempted tillage to extremely dense winter annual fields walk away extremely frustrated with the quality of their work and have left the soil surface uneven and difficult to plant into.  A uniform seedbed is extremely important in achieving adequate emergence.

2. Winter annuals will harbor insects in the spring.  Black cutworm is one of these insects.  Black cutworm moths migrate to the Corn Belt from coastal areas of the Gulf of Mexico early in the spring.  They deposit their eggs in fields with low, dense vegetation, such as chickweed, henbit and curly dock.  Fields that have dense early spring weed cover are much more likely to attract black cutworm moths.

3. Purple deadnettle and several other winter annual species appear to serve as alternate hosts for soybean cyst nematode.

The next step is to begin scouting the fields that will be planted to corn in 2012.  Fields with uniform infestations of winter annuals may benefit from burndown or tillage treatments made well ahead of planting.  The earlier the treatment, the easier the weeds should be to control and the less biomass developed.  If planting is delayed due to a wet spring, there will be large benefits to early control.  In early March growers need to assess their fields, determine weed size and density, and if fields are dry enough for applications.   If these conditions are observed they may need to get burndown or tillage treatments performed earlier than normal.  2012 is not a year to let these weeds get away.

References:
Purdue University – “Mild winter likely to increase insect, weed pressures”  February 16, 2012
The Ohio State University – “Weed Control Guide for Ohio Field Crops”  Bulletin 789
Iowa State University Extension – “It’s Time to Scout for Winter Annuals”  March 18, 2010
Purdue Extension “Winter Annual Weeds and Soybean Cyst Nematode Management”

Corn planting is fast approaching once again and plans are being finalized.  As we reflect on what we learned in 2011, we must not overlook the increased levels of corn rootworm experienced across the Midwest.  In isolated cases, higher root feeding on transgenic corn was noted by growers.  Iowa State’s Aaron Gassmann visited four fields in NE Iowa, researched the increased level of feeding and recently published a paper “Field-Evolved Resistance to Bt Maize by Western Corn Rootworm” in response to his findings in those four fields.  This newsletter will address the article and offer suggestions for the 2012 crop and beyond.

Abstract of Gassman Paper:

Methodology/Principal Findings: “We report that fields identified by farmers as having severe rootworm feeding injury to Bt maize contained populations of western corn rootworm that displayed significantly higher survival on Cry3Bb1 maize in laboratory bioassays than did western corn rootworm from fields not associated with such feeding injury. In all cases, fields experiencing severe rootworm feeding contained Cry3Bb1 maize. Interviews with farmers indicated that Cry3Bb1 maize had been grown in those fields for at least three consecutive years. There was a significant positive correlation between the number of years Cry3Bb1 maize had been grown in a field and the survival of rootworm populations on Cry3Bb1 maize in bioassays. However, there was no significant correlation among populations for survival on Cry34/35Ab1 maize and Cry3Bb1 maize, suggesting a lack of cross resistance between these Bt toxins.”

Conclusions/Significance: “This is the first report of field-evolved resistance to a Bt toxin by the western corn rootworm and by any species of Coleoptera.  Insufficient planting of refuges and     non-recessive inheritance of resistance may have contributed to resistance. These results suggest that improvements in resistance management and a more integrated approach to the use of Bt crops may be necessary.”

Which Trait Contains Cry3Bb1 Protein?
Cry3Bb1 is the protein expressed by YieldGard Rootworm (RW) or VT3 technology from Monsanto.  Figure 1 shows the current RW traits and associated protein expressed.  RW resistance was  confirmed in four Iowa continuous corn fields that were planted to the same RW trait for several years - VT3 with a single mode of action protein (Cry3Bb1).  The article states Cry3Bb1 hybrids have exhibited resistance compared to other trait platforms – this can be explained due to selection pressure – VT3 being used in the selected fields over the past several years.  The rootworm population in sampled fields was not exposed to other trait/protein options in prior years.  Like VT3, other RW trait platforms have encountered significant feeding in several University of Illinois RW testing trials over the past few years.

Resistance in Illinois?
Dr. Gray, University of Illinois Extension Entomologist, has not confirmed any resistance in Illinois to date, but feeding on VT3 was acknowledged in 2011.  Similarities exist from fields of Gassman’s study and those in Illinois with significant feeding—continuous corn, use of VT3 technology for several years, and no refuge used. Beetles were collected from a few select NW Illinois fields and sent to Aaron Gassman at Iowa State.  The same testing protocol will be utilized with this population as the Iowa population of resistant rootworm to determine if resistance is indeed occurring in Illinois.

High Population = More Feeding
Corn rootworm pressure has increased substantially in 2011 compared to previous years.  Figure 2 shows the areas where beetle numbers are most significant, although they vary significantly by field.  Larvae must feed to ingest protein.  Higher populations of  larvae results in higher levels of feeding and injury to corn roots, but does not confirm resistance has occurred.  Illinois Department of Crop Sciences documented extremely low densities of RW beetles overall the past few years.  Counts done July 27-28, 2011 show the average number of beetles per plant (Figure 3). The two  highest counties were Lee (0.64) and McLean (0.81). An economic threshold would  typically be 0.75 beetles per plant.  The use of traits and saturated conditions during hatch may have a direct effect on beetle number as well as fungicide/insecticide tank mixes that have increased the past few years.

Several thoughts exist why higher populations and feeding by corn rootworm occurred in 2011.

A dry fall in 2010 led to eggs being laid at varying depths. This extended larvae hatch well into the summer of 2011, longer than normal.
Aggressive tillage conducted in the fall of 2010 provided extremely mellow soils allowing larvae to  move about easily. 
Larvae mortality rate was low compared to the spring of 2009 and 2010.  Egg hatch did not coincide  with saturated soils as it did in 2009 & 2010.
The RW trait is a low dose technology.  Adequate protein must be produced by the plant to protect  root systems.  Under stressful conditions (dry soils, excessive heat, nitrogen deficiency etc.), protein        expression can be affected.

Adaptation

Corn rootworm has shown its ability to adapt to past management strategies.  Examples would include resistance to soil insecticides (chlorinated hydrocarbons), resistance to insecticides for adult  control in Nebraska, the development of the western corn rootworm soybean variant (lays eggs in soybean instead of corn fields), and the ability of the northern corn rootworm to exhibit extended diapause (eggs hatch two to four years after deposition) defeating crop rotation as a lone control measure.

Root Ratings of Hybrids Containing Cry3Bb1

A study conducted in 2005 by University of Illinois, in   cooperation with Monsanto, compared root ratings (0-3 scale) between nine different products containing the Cry3Bb1 protein for rootworm control.  Root injury     generally was greater with the August 10th rating compared to the July 20th date, but insignificant.  Two hybrids – C and D – were never commercialized.  Monsanto acknowledged that Hybrid E and H were the same after the study was complete.  The results of this study shows that variability in root protection does occur between hybrids containing Cry3Bb1 and likely occurs with other RW trait platforms.

Insecticide on Traited Hybrids

Rootworm control options with multiple modes of action may provide improved larvae control if beetle populations last fall were greater than expected.  However, a blanket treatment across the entire farm or in crop rotation systems may not be necessary and most likely not justified economically.  A positive yield response may not occur in every situation as shown in Figure 4.  A long term integrated approach to rootworm management is critical to provide adequate control of RW and maintain efficacy of all rootworm control options available today.

Recommendations for 2012

Moving forward, traits containing Cry3Bb1 will still provide good results on most acres.  Any reduced efficacy or resistance to the technology has been extremely localized in 2011 and should not be considered a Corn Belt wide problem.  However, growers should consider utilizing a pyramided approach (multiple modes of action) to rootworm management in fields with greatest risk for high RW populations, specifically continuous corn acres. A pyramided approach would include the use of Genuity SmartStax (STX) technology with multiple modes of action against rootworm or utilizing granular insecticide with VT3 or VT3Pro.

References:
Gray, M & Steffey, K. YieldGard Rootworm Performance:  Is Root Protection Equal Among These Transgenic Hybrids?  University of Illinois Extension. The Bulletin November 11, 2005. Issue No. 24/Article 2 .

Gray, Mike.  Survey of Illinois Corn Fields Reveals Exceedingly Low Densities of Western Corn Rootworm Adults.   University of Illinois Extension.  The Bulletin August 5, 2011.  Issue No. 18/Article 1.

Goss’s Wilt’s Impact on Ohio

Goss’s Wilt is one of the most devastating and feared leaf disease a corn grower can experience.  With the devastation comes many fear mongers and those wanting to make the disease into something it is not.  There have been several “reports” of finding Goss’s wilt in Ohio corn fields in 2011, but no confirmed cases to AgriGold’s knowledge.  All the cases have been a case of misidentification.  Even though there are no cases of Goss’ Wilt in Ohio, nor does AgriGold believe there will  be for several  years, some background information and how to identify the pathogen should help extinguish any false rumors and/or fears.

Goss’s Wilt was first observed in Nebraska more than 40 years ago.  For much of that time, the disease seemed to be content in Nebraska but beginning in 2008 it began to march eastward into Iowa, Illinois and Indiana.  Since that time Goss’s Wilt has continued to grow exponentially in the I-states, most notably Iowa and Illinois.  The map detailed in Figure 1, was put together by AgriGold agronomists and details where Goss’s wilt is most prevalent.

Figure 1.  Where is it?  2011 map of Goss’s wilt and its disease severity across the corn belt.

Red-Severe infestation

Orange- Moderate infestation

Yellow- Low infestation

Disease Development and Identification:

The pathogen that causes Goss’s Wilt overwinters in crop residue and serves as the primary inoculum source.  As the young plants are damaged by wind, hail or heavy rain the bacterium enters into the plant via a wound and can cause two types of symptoms.  The most common symptom is water-soaked lesions that appear on the leaf and glisten in the sunlight.  Goss’s wilt lesions tend to have wavy or bleeding margins between healthy and diseased tissue as seen in Figure 2.  The foliar lesions can progress and kill large areas of the canopy thus significantly reducing the photosynthetic capacity of the corn plant.  The other, less common symptom occurs when the xylem tissue within the stalk becomes discolored and slimy causing the plant to conduct water less effectively.

Figure 2.  Goss’s Wilt Leaf Blight.  Notice the shiny, water soaked appearance with wavy/bleeding margins.

Goss’s Wilt is easily confused with another corn disease, Northern Corn Leaf Blight (NCLB).  NCLB is identified as a gray lesion that is in the shape of a cigar.  Figure 3 shows the two diseases side by side to compare the differences.

Figure 3.  Northern Corn Leaf Blight symptoms compared to Goss’s Wilt symptoms.

Effects on Yield

Yield losses have been documented from both the wilt and leaf blight phases of the disease, however it has been difficult to quantify.  The reason for the difficulty is that timing plays a major role in how much yield is negatively impacted by Goss’s Wilt.  If a corn plant is infected early in the growing season versus late in the growing season, there is a higher chance for significant yield loss.  Also if weather conditions continue to be favorable, high humidity along with warm temperatures of at least 80°F, there will be more yield loss that will be associated with Goss’s Wilt.  Therefore if the disease moves onto the corn plant late and/or the favorable weather conditions are short term, little or no yield loss will be associated with Goss’s Wilt. 

Using Best Management Practices (BMP) to Control Goss’s Wilt:

• Tillage, Crop Rotation, Fungicide/Bactericide Applications and Hybrid Selection.

Tillage and Crop Rotation

The two most common measures to control disease is tillage and crop rotation.  Tillage has been shown to help reduce the occurrence of Goss’s Wilt, but does not completely eliminate the pathogen.  Research has shown that pure cultures of the bacterium did not survive long in bare soil; however, the bacterium was able to survive for up to 10 months in the surface on corn residue.   When the residue was buried the pathogen was still found in the stalks after 10 months but at reduced levels.  Using tillage methods that bury infected residue should reduce the survival of Goss’s wilt and the rate of new infections.

Crop rotation is the next defense against Goss’s Wilt.  The bacterium that causes Goss’s wilt is enhanced in fields of continuous corn.  Rotating to a non-host crop such as wheat or soybeans will allow time for the infested residue to further break down and inoculum levels to decrease.  The effect of crop rotation is evident when looking at the map (Figure 1).  Areas like southern Iowa and Northern Missouri do not have Goss’s wilt occurring at a very high rate because the majority of acres in these areas are rotated and not continuous corn.  Both tillage and crop rotation will help decrease the severity of Goss’s wilt but do not guarantee complete freedom from the disease showing up.

Fungicide and Bactericide

Goss’s wilt is different from other corn leaf diseases in that it is a bacterium not a fungus.  Because Goss’s Wilt is a bacterium, foliar fungicides do not prevent the infection nor cure it.  To control bacterium, a bactericide must be applied.  Bactericides have long been used in citrus and potato crops, but never in corn.  Currently, the agricultural industry is skeptical that bactericides are a viable option to stop Goss’s wilt, due to their cost and the number of applications thought to be needed for complete protection.  There is currently no documented result of bactericides being an effective control method of Goss’s Wilt on corn plants.

Hybrid Selection

The best method to control Goss’s Wilt is by selecting resistant hybrids.   Many seed companies have made it a priority over the last couple years to select and advance hybrids with improved Goss’s Wilt tolerance.  AgriGold has been a leader for germplasm resistant to Goss’s Wilt.  AgriGold’s research station in Kearney, NE was where we first began to rate our germplasm years ago.  As the disease has moved eastward our research stations in Ames, IA and Champaign, IL have increased their selections as well.  Currently our research personal are inoculating select experimental trials with the Goss’s Wilt bacterium when the corn is 12” tall.  To properly inoculate the plants, researchers  simulate hail by creating a wound to the plant and then apply the bacterium at 2 different times, 1 week apart.  The hybrids are then evaluated in late summer and their tolerance levels recorded.   Agrigold also uses its agronomy team to record and fine tune each hybrids rating across our marketing area.

Currently AgriGold uses a 1-10 scale to rate for Goss’s wilt.  The lower the rating the more susceptible the product is to Goss’s wilt.   Many of Family B hybrids rate very tolerant to Goss’s wilt and hardly show any presence of the disease even under high pressure.   While our Family F’s tend to be more susceptible to Goss’s Wilt.  AgriGold has been working to identify hybrids in the Family F genetic pool with good to high tolerance.  Figure 4, shows the drastic difference hybrid selection can have on the negative effects of Goss’s Wilt.

Summary

2011 has proven too many corn growers that Goss’s wilt is here to stay.  The rate and area of growth in 2012 is unknown but fully expected to expand to the East and South.  The extent of yield loss on the infected acres will drastically depend on the timing of the infection and the timing of the weather after infection.    As of right now, there are no fungicides/bactericides documented to cure or stop infections of Goss’s wilt.  Therefore looking for other avenues to control and/or manage Goss’s Wilt will be important in 2012.  Crop rotation and tillage will reduce the pathogen but not guarantee that Goss’s wilt will completely be eradicated from the field.  Ultimately, hybrid selection is the best way to defend against Goss’s Wilt.  AgriGold is continuing to select hybrids with yield and good Goss’s wilt tolerance.   For 2012, we have a very strong lineup that brings unmatched Goss’s wilt tolerance in the industry and high yields.  With proper hybrid selection and placement Goss’s Wilt’s impact can be reduced in the future.

Zinc is a micronutrient, meaning it is needed in very small amounts by the corn plant.  Actually the amount is measured in ounces per acre instead of the normal pounds per acre of other major nutrients such as nitrogen and potassium.  A 150 bushel corn crop is known to remove only 0.25 pounds of zinc.  Even though zinc is needed in small amounts, it has a huge impact on how a corn plant grows and ultimately how much yield is produced.  In a study performed by the University of Nebraska on a low zinc testing soil showed a 53 bushel increase in yield by adding one pound of zinc to a starter.

Role of zinc in a corn plant:

Zinc plays a critical role in the following systems of a corn plant:

• Aids in the synthesis (production) of growth hormones and proteins.
• It is needed in the production of chlorophyll and carbohydrate metabolism.
• It is essential for the transportation of calcium throughout the corn plant.
• Necessary for cell elongation, the increase in leaf and node size along with grain formation.

Factors that Effect Zinc’s Availability:

1. Soil pH:  The availability of zinc decreases as pH increases, the ideal range for availability is a soil pH between 5.0 and 7.0.  A soil pH above 7.0 causes zinc to form compounds that are unavailable to plants and thus will show more zinc deficiency symptoms.
2. Organic Matter:  Zinc is often attached to the soils organic matter and easily accessible by the corn plant.  Soils that are low in organic matter have less zinc available and deficiencies are often seen on these soils.  Sandy soils and/or highly eroded soils are typically low in organic matter and first to show deficiencies.
3. Growing Conditions:  Uptake and availability of zinc can be negatively affected by cool, wet and overcast conditions early in the growing season.   The temporary deficiency is caused by slow root growth.  The slow growing root system is often not able to meet the early season needs of the corn plant.   As the temperatures rise and conditions improve, deficiency symptoms should disappear.
4. Soil Compaction:  Soils that are compacted significantly reduce the corn plants rooting ability.  With the lack of roots, the chance of intercepting zinc minerals is reduced and the corn plant is easily put into a zinc deficient state.
5. Soil Phosphorus Levels:  The uptake of zinc is increased as the soil levels of mycorhizae, a root-associated fungus, increase.  When phosphorus levels increase, the mycorhizae population decreases, thus reducing the plants ability to uptake zinc, therefore high soil phosphorus levels tend to reduce the availability of zinc.  Phosphorous levels that are higher than 90 lbs/acre are likely to benefit from additional zinc applications.

Zinc Deficiency in Corn:

The most common symptoms associated with zinc deficiency in corn results in a white or yellow band that runs parallel with the mid rib. Other problems associated with zinc deficiency include:

• Poor root development
• Stunted growth
• Small leaves
• Shortened internodes
• Delayed silking and tasseling
• Chalky kernels

There is also the hidden deficiency that has no symptoms.  Hidden zinc deficiencies are well documented in corn and reductions in yield can be up to 40%.  Therefore the best method to determine if zinc is deficient is by taking soil samples to determine the levels of zinc in the soil.

There are typically two methods of applying zinc to a field either by a broadcast application or a banded application done typically at planting.  While there are positives to both application methods, the most preferred method of application occurs via banding.  Due to the small amounts that are applied, the chances of roots coming into contact with the applied zinc are far greater in a band verse broadcast applications.

Conclusion:

Zinc is one of the most important micronutrients for a high yielding corn crop.  Through proper soil testing and the willingness to address any deficiencies through proper fertilization, zinc deficiencies can be addressed and corrected.  High yielding corn is the goal of every corn grower and zinc could be the missing key to obtaining those yields.

Source:
Johnson, Jay; “Most Asked Agronomic Questions;” Bulletin 760, Chapter 2: Starter Fertilizer;  The Ohio State University
Potash & Phosphate Institute; “Soil Fertility Manual;” 1999
Rehm, George; “The Mighty Micronutrients;” University of Minnesota Extension
Rehm, George, Schmitt, Michael; “Zinc for Crop Production;” University of Minnesota Extension; 2002
Sahota, Tarlok; “Zinc is Important for Corn;” Certified Crop Advisor Newsletter
Terra Industries Inc; “Secondary Nutrient & Micronutrient Handbook.” 

By:  Steve Woodall, Production, Production Contract Administrator, AgReliant Genetics

AgReliant Genetics, AgriGold’s parent company, is in charge of producing the highest quality seed possible and ensuring AgriGold’s customers have the right hybrids in the trait package they desire.  Due to the speed and complexity that is involved in hybrid corn seed production, AgReliant relies on winter production in South America to help strengthen their seed supply for this growing season and many more to come.

Producing seed corn in South America for U.S. corn growers offers some unique benefits and challenges.  AgReliant produces seed in Argentina and Chile for several reasons.  Genetics and traits in the seed industry are moving ahead faster now than they ever have.  Having a second production cycle each year offers the opportunity to provide our customers with a better supply of the newest products and also gives the chance to increase supply of our best products.  Parent seed is also produced in South America in order to bring new products up to commercial production levels faster.

A common practice for winter production is for parent seed produced in the U.S. to be harvested, conditioned, quality tested, shipped to South America and planted in a matter of a few weeks.  The parent seed traveling to South America is flown down on commercial passenger flights and regular air freight lines.  From the time the seed leaves the AgReliant Genetics parent seed plant until it is planted can be as short as five days.

Why Argentina and Chile?  Argentina offers an arid climate similar to the western United States and is very well suited to produce 105 day and later maturity hybrids.  It also offers vast growing areas where large fields and widespread isolations are possible.  All seed production fields in Argentina are irrigated to insure against extended dry periods.  The Argentina producers used by AgReliant are equipped with modern dryers and facilities to provide the same gentle handling and high quality seed that can be produced here in the U.S.  The widespread growing areas are often served only by dirt roads and the harvest season tends to be rainy some years.  The transportation system sometimes causes delays in harvest, but rarely more than a day or two.  The dirt roads are well drained and packed harder than many paved roads and trucks are back on them within a few hours of the rain stopping.

The climates in Chile are suitable for early season hybrids and offer the same isolation opportunity as Argentina because of the widespread fruit and vegetable production.  Many of the seed fields are part of vegetable rotations.  The fields in Chile tend to be smaller due to the geography and Chilean farmers also tend to operate on very few acres.  Due to the climate in Chile being very stable but dry, irrigation for all crops are necessary.  The water supplies for the irrigation are systems of reservoirs and channels that capture snowmelt that are then used for flood irrigation.  Pivots are becoming more common in Chile, fed by the same channels.  Transportation issues are also a challenge in Chile, but for different reasons than Argentina.  The roads that serve the farms are narrow, winding and gravel, thus not allowing the use of large equipment.  Most farms operate with 60 horsepower and less tractors, 4 or 6 row equipment and trucking is all done with straight trucks. 

Once the seed fields are harvested, the processing equipment and quality standards are identical to the U.S.’s facilities.  In both countries, harvest begins around the first of February and lasts into March.

Seed corn is harvested and dried on the ear and shelled at 12% moisture.  After shelling the dried kernels off of the ears, they are packaged into poly bulk bags (the same polybags that are sometimes used for soybeans) and are containerized for shipping back to the U.S.  A vast majority of seed containers are shipped back using ocean freight due to the quantities involved.  A freight liner from Argentina takes 25-30 days to arrive in the U.S.   Shipping from Chile averages a faster travel time of 13-19 days because of the access to the “fast boats” that are used for shipping fresh fruits and vegetables.  Upon arrival at the U.S. port, the containers are unloaded and sorted so AgReliant can selectively send different lots to different AgReliant plants depending on geography and customer’s needs.  From the U.S. port to the plant varies from 1 to 7 days depending on customs clearance and the volume of seed coming in on any specific vessel.  Samples of each seed lot are flown back the AgReliant Quality Assurance lab for testing while the bulk of the seed lot are still in transit.  By taking the extra expense to fly samples back the U.S. prior to the ships arrival allows AgReliant to have the quality analysis done before the freight ships arrives in the U.S., expediting delivery to our customers.  In a best case scenario, seed arriving in the port on Friday could be in a customer’s planter in less than 1 week.

Winter production in South America requires intensive management and coordination from the Sales, Foundation, Production and Quality departments here in the U.S. and with our growers in South America.  Everyone involved is committed to ensuring that our customers are supplied with the best products in the seed industry and the best quality possible on a timely basis.  Next time you hear that your seed is being produced in South America, take a moment and reflect on the challenges and opportunities that are associated with winter production.