How to Preserve Fall Applied Nitrogen Through the Winter

As we start making nutrient program decisions for the coming year, nitrogen (N) is a nutrient that requires special attention. Preserving fall applied N through the winter is crucial for crop success. Nitrogen is a key corn nutrient when trying to maximize yield potential; however, it can be one of the toughest nutrients to manage because it doesn’t always stay in place.

There are different ways N can be lost but the three most common are leaching, denitrification, and volatilization. Leaching is when nitrate and nitrite move below the root zone with water flow. Denitrification occurs when nitrate and nitrite are converted to gaseous forms when soils are saturated for several days. Volatilization is when ammonium remains on or near the surface and is lost as a gas.

Cover crops can be used to absorb unused soil N from the current crop. Brassicas, such as oilseed and forage radish are very good for N absorption; however, they are not winter hardy and can start releasing N during their decay. Cereal rye and other winter hardy cover crops can hold absorbed N in plant tissues through the winter; however, after termination, N is not immediately available to a new crop because the plants must decompose to release N.

The most common source of N used in the fall is anhydrous ammonia, but this source and timing needs to be managed properly to ensure crop availability in the spring. One of the keys to preserving applied N through the winter is keeping it in the ammonium form to prevent it from leaching. Appling anhydrous ammonia when soil temperatures are under 50° F is one way to help keep it in the ammonium form. Therefore, being attentive to the forecast can help decide when to apply. In areas where winter soil temperatures are usually above 50° F, anhydrous should not be applied.

Another way to keep anhydrous ammonia in the ammonium state is to utilize a nitrogen stabilizer. The purpose of stabilizers is to stop the ammonium from converting to nitrate.  There are many types of nitrogen stabilizers; therefore, find one that adapts best to your operation.

These are a couple ways to help preserve fall applied N through the winter. Make sure you apply under proper weather and field conditions and use an effective stabilizer. Nitrogen is valuable to your corn crop and costly; therefore, it is important to keep it available for the next growing season.

David Trainor

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