Side Dress Considerations

BY Dairyland Seed Agronomy Team

2023 Corn In Season Nutrient Management

As corn planting wraps up across the Dairyland Seed footprint, sides dress application of nitrogen will begin soon, and in many cases has begun. There is no “one size fits all” nitrogen management program. Variables such as soil type, type of nitrogen fertilizer applied, application timing, etc. all have an impact on determining total program.

When does nitrogen use peak in corn? On average, N use peaks in corn between the V6 and R1 (silking) growth stages. Corn will accumulate 70 percent of nitrogen that it will need during this period. Nitrogen availability during this time is critical for corn growth and development. The nitrogen stored in the plant during vegetive growth is remobilized during maturity and can account for over half of the N found in the grain.

How much N to apply? Nitrogen use efficiency in corn has increased over the last 50 years as illustrated by the graph. Factors such as N products used, application timing, and efficiency of modern hybrids play a role in this increase in efficiency. As shown by the graph, 1.1 to 0.8 pounds of N are required to produce a bushel of grain. It is important to note that the graph refers to total N applied to the corn crop -- not just side dress application.

Pounds of N applied/Bushel of Grain Produced

What about Nitrogen stabilizers? A nitrogen stabilizer is a product added to Nitrogen fertilizer that keeps the N in the most stable, ammonium (NH₄⁺) form for a longer period. The ammonium form of Nitrogen is not mobile in the soil, but through nitrification, ammonium is turned to nitrate (NO₃^-) which is mobile in the soil and prone to leaching or denitrification.

The two types of nitrogen stabilizers are urease inhibitors and nitrification inhibitors. Urease inhibitors are added to surface-applied nitrogen fertilizers to inhibit ammonia volitation or “gassing off”. Nitrification inhibitors are added to incorporated nitrogen fertilizers and work to inhibit the biological activities that turn ammoniacal nitrogen to nitrate. Nitrate is mobile and prone to leaching through the soil profile. Corn can use both ammonium and nitrate forms of Nitrogen. Each of these stabilizer additives work to keep the fertilizer where you put it and keep it available to the crop for a longer period.

Take note: Side dress is an excellent time to monitor the condition of your corn crop. Some notes to take while side dressing are listed below.

Herbicide efficacy: Were there any escapes from your herbicide application?
Planter issues: Are there any discernable patterns such as skips or stand variations that can be linked to possible planter issues? Noting these issues now, and performing necessary planter maintenance, can help prevent these issues next year.
Insect feeding: Above ground pest feeding can be obvious from a tractor cab, but abrupt changes in corn plant height and off color or pale corn plants can mean that pests are feeding below the soil surface. Often damage from Asiatic Garden beetles and other root feeding pests can be assessed while side dressing.