Nitrogen is a vital nutrient for corn production, as it plays a crucial role in corn growth and development. It makes up proteins, enzymes, and chlorophyll, all of which are important for plant growth and photosynthesis. It promotes leaf and stalk development, enhances the plant’s ability to utilize other nutrients, and improves overall plant health.  

Nitrogen sidedressing is just one way farmers can get this vital nutrient to their corn plants.

Understanding Nitrogen Sidedressing  

Sidedressing is where additional nitrogen fertilizer is applied to corn after the initial planting. It helps to supplement the nitrogen available to the plants, ensuring optimal growth and maximizing yields.  

It’s better to sidedress as a planned application rather than a rescue application. Planning ahead allows a farmer to save money by buying early — and avoid scrambling to get the materials for a rescue application mid-season.

Nitrogen can be sidedressed using a few methods:  

• Urea Ammonium Nitrate (UAN): Can be applied with a sprayer that has drop nozzles that prevent leaf burns and dribbles onto the soil surface.  
• Anhydrous Ammonia: Must inject into the soil using injection knives, typically placed at a depth of six to eight inches. The placement depth minimizes ammonia losses to the atmosphere and ensures efficient uptake by the corn roots. Also, it needs to be applied in well-drained soils with good moisture levels.  

How to Time Nitrogen Sidedressing 

To optimize nutrient availability, maximize crop uptake, and minimize nitrogen losses, nitrogen application timing is critical. Here are some key reasons why:

• Crop growth and development: Timely nitrogen application guarantees an ample, easily accessible nutrient supply precisely when the crop requires it the most. This means farmers can enhance root development and facilitate the reproductive process—which ultimately enhances crop yield and improves quality.  
• Nutrient demand: For a nitrogen application, aim for the V6 growth stage, where corn is much smaller. Applying all nitrogen at planting creates a longer timeline and increases the risk of loss. In V4-V5, the plant has used only roughly 10% of the total nitrogen. So nitrogen needs to be applied before V8 to maximize nitrogen uptake. This allows the nitrogen enough time to convert to usable forms by V8-V9. 
• Minimizing nitrogen losses: Applying all nitrogen during initial planting increases the risk of leaching or denitrification. Denitrification involves bacteria converting nitrates to nitrogen gasses that quickly leave the soil. Another avenue for nitrogen loss is volatilization, which occurs when urea-based nitrogen on the soil surface quickly converts to ammonia gas and evaporates. 

Sidedress Techniques 

Sidedress applications help supplement the plants’ nutrient needs when the initial fertilizer application is insufficient. Sidedressing can provide a targeted nutrient boost, which improves crop growth, development, and yields.  

• Dribbling: This technique has the advantage of adding nutrients directly at the base of the plant. Dribbling urea ammonium nitrate (UAN) can also greatly speed up the application process and allow a wider window for application.  
• Injection: The urea portion of UAN is the most susceptible to loss. But the risk of that loss decreases when it’s injected into the soil. Just make sure the soil moisture isn’t too high. If the soil doesn’t crumble when squeezed, there’s a higher risk of slicking the sidewalls and not closing the furrow properly. This can leave an open trench, which means both roots will try to access the nitrogen. For farmers using anhydrous ammonia, this product can only be injected into the soil.  
• Broadcast: It’s not recommended to broadcast spray UAN over the top due to leaf burning. 

Understand why sidedressing is important 

Sidedressing is a great way to maintain flexibility within an operation. If a farmer loses nitrogen before planting (through runoff, volatilization, etc), sidedressing provides the opportunity to add more of this important nutrient. 

Ultimately, the bottom line is:   

• Optimal yields at harvest time directly depend on the availability of nitrogen, a vital nutrient for crop growth. Sidedressing can be an effective method of getting that nutrient directly to the plant.
• Which sidedressing technique to use will depend on an operation’s landscape and needs.  
• To optimize an application, sidedress during the V6 growth stage.  

If you’re considering a nitrogen sidedressing application, our agronomists  are available to answer questions and address concerns.