Combined Application of Concentrated Vinasse and Nitrogen Fertilizers in Sugarcane: Strategies to Reduce Ammonia Volatilization Losses

Ethanol is an alternative source of renewable fuel, but increasing production of vinasse as a by-product requires proper management. Combining concentrated vinasse (CV) and nitrogen (N) fertilizer into a single operation is increasing in Brazil. However, the chemical stability and potential for volatilization losses remain unknown. Our objectives were to characterize the chemical stability of CV and N fertilizer mixtures and to evaluate volatilization losses following application to sugarcane trash. In an initial study, we monitored variations in pH, total N and inorganic N content after a 22-day incubation of mixtures of CV and N fertilizer. In a second study, we evaluated N-NH3 volatilization losses following surface application to sugarcane trash. We used a medium-textured soil covered with trash (8 Mg ha(-1)), and measurements of N-NH3 losses were taken using acid traps in semi-static chambers during 40 days after mixture application. The addition of urea to the CV did not increase the pH and resulted in the maintenance of N in amidic form, demonstrating the chemical stability of the mixture. However, after application to sugarcane trash, N losses from urea added to the CV ranged from 29 to 35 % of the applied N. The addition of phosphoric acid and boron has the potential to reduce the N loss of 26 % of the applied N. The use of UAN mixed with CV had the lowest loss through volatilization (21 % of applied N) and is the suggested to use for application to sugarcane trash.