Timing of Nitrogen Side-Dress Applications

Four-Minute Read Time | Nitrogen Advice

Nitrogen SideDress Application

Nitrogen (N) is the most important plant nutrient in determining the final grain yield, and having adequate N availability in corn allows the plant to reach its genetic yield potential. But end-of-the-season success doesn’t come cheap as N is a major investment in corn production.

Applying the right amount of N at the right time can help you get the highest return on your investment.

But first, it’s important to understand when a corn plant uses N in its development stages.

Nitrogen Uptake in Corn

Corn needs little nitrogen during early vegetative stages to about the fifth leaf development stage. N is taken up by the plant throughout its active growth.

Corn Growth in Vegetative State

If you need a refresher in the vegetative stages of corn growth, check out this article.

N uptake accelerates at the vegetative V6 (V6) growth stage, at which time 25 to 30 pounds of N has been taken up by the plant. 

Through V6 to V12, about 25% of the total N is taken up by the plant.

From V12 to the emergence of the tassel (VT), about 40% of the total N needed is taken up. 

The remaining N needed is taken up from tassel emergence until the reproductive stage 3 (R3).

Nitrogen uptake is mostly done shortly after pollination.

A shortage of N at emergence until V6 can result in a weaker root system, particularly after V4 as the plant makes the transition from seed resources to soil-based resources.

During V6 to V18, when the stem is actively elongating, if adequate N is not available, vigor can be reduced, the root system can be stunted, and the uptake of other nutrients (particularly potassium) may be reduced. This can have negative consequences for photosynthetic efficiency.

A decrease in photosynthetic activity can reduce kernel numbers and, if severe, result in kernel abortion. Kernel row number is determined by V8, and an N deficiency before this stage will reduce the  number of kernel rows.

Additionally, N deficiency during grain fill can result in remobilization of N from the stalks and roots to the developing kernels. This can result in weak stalks, leading to infection by stalk rot organisms.

Researching N Side-Dress Timing

The Bayer Learning Center at Monmouth, Illinois, has been conducting trials over the past four years to evaluate the impact of N side-dress timing.

Through our 2019 testing, side-dressing N at V4 resulted in significantly higher average yields than later timings.
Timing of Sidedress Application

It’s important to remember that the ideal timing of later-season N applications can change from year to year due to weather and environmental conditions. While all timing options can vary, not getting the right amount of N applied can be a much greater concern.

The Best Options for Side-Dressing N

Injection into the soil or dribbling the N fertilizer between rows are the best ways to side-dress because this application can reduce volatilization of urea and protect the crop from foliar damage.

If ammonia is used for the application, it is important to watch soil conditions to ensure that the knife track closes properly to avoid foliage damage by free ammonia escaping to the atmosphere.

At Channel®, we’re committed to helping our farmers maximize performance and profitability through our research and studies. By providing insights and advice, we’re able to help our customers make the most out of our elite seed products.

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