EVALUATION OF N ADDITIVES FOR IMPROVING N USE EFFICIENCY OF SURFACE APPLIED UREA TO DRY SEEDED AND PERMANENTLY FLOODED RICE

There are several potential Nitrogen (N) loss mechanisms in a dry seeded and delayed flood system rice (Oryza Satvia L.) production system including urea volatilization and denitrification. The scope and magnitude of these potential losses are largely weather dependent. Two additives (stabilizers), Agrotain and Nutrisphere-N, have been offered to rice producers for controlling these potential losses. This study compared these two products in their ability to maintain rice grain yields, where cultural management maximizes these loss mechanisms. Response of rice to urea-N stabilizers varied in 2007 and 2008 depending on soil and environmental conditions. In 2007, dry soil surface at time of urea-N application and lack of rainfall resulted in a low loss due to N volatilization. However, urea-N volatilization or denitrification were higher in 2008 and using Agrotain stabilizer resulted in higher yields of rice at 78 kg N ha^-1. Across years, Agrotain and Nutrisphere-N were similar in terms of slightly improving rice grain yields compared to untreated urea at the rate of 78 kg N ha^-1. Therefore, urea stabilizers may offer a good solution in years with high potential for urea-N losses.