Ammonia volatilization and yield of corn fertilized with different nitrogen sources in the Brazilian semiarid

The objective of this work was to evaluate the effect of the use of different nitrogen fertilizers on N losses by NH3 volatilization and on the grain yield of a corn (Zea mays) crop grown in the semiarid region of the state of Sergipe, Brazil. Corn was managed under rainfed conditions and conventional tillage. The fertilization treatments were: sulfur-coated urea (SU) and organo-mineral-coated urea (OMU). Regular urea and ammonium sulfate (AS) were also included as a reference of N sources of high and low NH3-volatilization potential, as well as a control without N fertilization. The N sources were applied to the soil surface at a rate of 150 kg ha-1 N as side-dressing at the V5 growth stage of corn. The experiment was carried out in 2015 and repeated in 2016. Losses of N through NH3 volatilization differed among the N sources in the two study years, with AS presenting the lowest N losses and regular urea, the highest. In the area treated with OMU, losses by NH3 volatilization were consistently controlled, showing a reduction of 74 and 67% in relation to that of regular urea in both years. SU, however, only mitigated NH3-N losses in 2015, increasing them in 2016, compared with regular urea. Corn plant grain yield and N status, assessed by the index leaf, did not clearly reflect N losses by NH3 volatilization. For the semiarid of Sergipe, OMU is the best urea-based fertilizer to mitigate N losses by NH3 volatilization, and the use of AS is an alternative to increase corn yield and eliminate N losses as NH3. Resumo: O objetivo deste trabalho foi avaliar o efeito do uso de diferentes adubos nitrogenados nas perdas de N por volatilização de NH3 e no rendimento de grãos de cultura de milho (Zea mays) na região semiárida do estado de Sergipe. O milho foi manejado sob condições de sequeiro e preparo convencional. Os tratamentos de fertilização foram: ureia revestida com enxofre (SU) e ureia organomineral (OMU). Também foram incluídos ureia comercial e sulfato de amônio (SA) como referência de fontes de N com alto e baixo potencial de volatilização de NH3, além de um controle não fertilizado com N. As fontes de N foram aplicadas na superfície do solo a uma taxa de 150 kg ha-1 de N, como cobertura, no estádio V5 de crescimento do milho. O experimento foi realizado em 2015 e repetido em 2016. As perdas de N pela volatilização de NH3 foram diferentes entre as fontes de N nos dois anos de estudo, com SA tendo apresentado a menor perda de N e ureia comercial, a maior.