Modeling of Nitrogen Losses Through Ammonia Volatilization in Second-season Corn

Knowledge on the behavior of cumulative N-NH3 volatilization is important for defining the strategies to reduce the N losses, as well as increasing the efficiency of nitrogen fertilization in different environments. The present study, which uses nonlinear models, aims at assessing the cumulative N-NH3 losses through volatilization by applying different rates of urea over time to two soils cultivated with second-season corn. Two experiments were carried out; one in a clayey Oxisol, and another in a sandy-clay loam Ultisol in a randomized block experimental design. N-NH3 volatilization was quantified by using semi-open static chambers and spectrophotometry (salicylate blue). The cumulative N-NH3 losses were similar at both rates of urea and in both soils assessed, ranging from 34.04% to 43.15% of the N applied. The highest N-NH3 volatilization occurred from 1.03 to 6.48 days after applying the fertilizer, and the highest volatilization rates ranged from 0.90 to 2.91 kg ha(-1) d(-1). The shortest time to reach the highest volatilization rate, associated with the highest daily rate of N-NH3 volatilization, was seen in the Ultisol. Although the volatilizations accumulated in both soils were similar, this result was only seen due to the climatic conditions after applying the fertilizer, which contributed to minimize the N-NH3 losses. The use of nonlinear models has shown an appropriate data adjustment, providing parameters that help to understand the behavior of N-NH3 volatilization accumulated over time in second-season corn.