ENID, Okla. —
Many parts of north central Oklahoma are faced with the potential for leaching or denitrification loss of nitrogen from fields planted or intended for corn and sorghum due to recent heavy rains.
With the warmer weather there is a greater potential for loss.
The leaching and denitrification processes are quite different, and normally occur on different types of soils and under different situations. But both involve the nitrate form of nitrogen. The nitrate-nitrogen present in fertilizers such as ammonium nitrate (50 percent nitrate) or UAN solution (25 percent nitrate), is immediately susceptible to leaching or denitrification loss.
Other forms of nitrogen have to be converted in the soil to nitrate-nitrogen before leaching or denitrification would become a problem.
Before estimating how much nitrogen may have been lost in wet soils from leaching or denitrification, producers should first try to get some idea of how much of the nitrogen they applied. This will help provide a better estimate of how much nitrogen may have undergone nitrification into nitrate at this point in the season.
Factors affecting nitrification
How quickly ammonium-nitrogen in soil converts to nitrate-nitrogen is a function of soil oxygen content, soil temperature, pH, how the nitrogen is applied and some characteristics of the fertilizer. Nitrification is an aerobic process and requires high levels of soil oxygen. Conditions that reduce oxygen supplies, such as wet soils, will inhibit nitrification and keep nitrogen in the ammonium form. Optimum soil temperatures for nitrification are in the range of 75-80 degrees. When urea or UAN are broadcast, nitrification will occur more rapidly than when those materials are banded. The nitrification rate of anhydrous ammonia is even slower, due to the impact of the ammonia on the organisms in the application band. The use of a nitrification inhibitor, especially with banded ammonia, will slow the process of nitrification even further.