Agronomy Alert: Nitrogen Management Decisions


With the recent heavy rains across a vast portion of our area, we need to take a good look at our nitrogen management. In many areas we have had multiple inches of rain, which has led to ponding and very saturated soils. In many cases we have lost a fair amount of our pre-plant nitrogen from these heavy rains. We are now beginning to see a substantial amount of yellowing on the hilltops and low areas, which is usually a sign of potential nitrogen (N) loss.


Nitrogen can be the most difficult nutrient to manage simply because it can move off the field as runoff, move quickly through the soil profile and leach, and it can be lost to the atmosphere through denitrification. All of those nitrogen loss pathways can happen under significant rainfall and can lead to substantial amounts of nutrient loss. Understanding nitrogen and how it works in the soil and the plant can help you make better management decisions.


There are many variables that interact to influence the potential for N loss from heavy rainfall. This makes it difficult to estimate the amount of fertilizer N that has been lost and to decide whether producers should apply more fertilizer. It is important to determine if the remaining N will be adequate to optimize your yield potential.

Carefully monitoring the crop for N status is especially important during the rapid growth phase through silking. Visual observations indicating N deficiency include yellowing in the lower leaves and an inverted V yellowing pattern of leaf tips. By the time N deficiency is visible, yield potential may have already been reduced.

Soil sampling is an excellent option to evaluate how much fertilizer is left in the soil. A soil nitrate test should always be considered before applying more nitrogen. If tests show a low value, then a side dress application would be economical. The timing of the application is also very important. The V6 stage is when a corn plant begins to increase the uptake of nitrogen exponentially. The application should be as close to this growth stage as possible to reduce stress on the plant as it begins to determine its ear size.

Photo Credit: University of Nebraska Lincoln, Institute of Agriculture and Natural Resources Crop Watch

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Nick Brandenburg

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