Effect of nitrogen sources on ammonia volatilization, grain yield and soil nitrogen losses in no-till wheat in an Argentine soil

Abstract

The ammonia losses under field conditions vary widely and these nitrogen losses can decrease crops yield. However, experiment with wheat in the Argentinean Pampas showed that yields are not related to the volatilization losses of several nitrogen fertilizers. We hypothesize that ammonia volatilization from urea was compensated with higher apparent soil mineralization rate and then, even with high ammonia volatilization from urea, wheat yields were not affected. We evaluated ammonia volatilization, apparent nitrogen mineralization, apparent nitrogen uptake efficiency, and their effects on wheat yields. The experiment was carried out with wheat grown in a no-till Typic Hapludoll, using urea, UAN and IBDU. Ammonia losses were 17.1% and 4.7% of N applied as urea and UAN, respectively; IBDU and control were low. Wheat yields were not affected by ammonia losses. The N uptake and N export was greater in fertilized treatments. For urea, the highest volatilization rate was compensated by the highest soil mineralization rate. From the sustainable agriculture point of view, the volatilization would be dangerous because the soil could tend to compensate that loss, thus impoverishing itself in native nitrogen.