Nitrogen (N) fertilization is the main source of greenhouse gases (GHG) emissions to the atmosphere in sugarcane cultivation, mainly due to nitrous oxide (N2O) emission. Some management practices of sugarcane production in Brazil may affect the rates of greenhouse gas emissions, such as the recycling of the waste generated during ethanol production (vinasse). Recent studies indicate that the application of vinasse (VNC), especially with the N fertilizers, results in increases on N2O emissions. Therefore, alternatives to reduce these emissions are necessary, particularly for the management of vinasse applied to soil. Understanding the interactions that determine field emissions of GHG under different vinasse management conditions may greatly contribute to the sustainable production of biofuels. The objective of this project is to evaluate emission of N2O, CH4 and CO2 during the sugarcane ratoon cycle after VNC and vinasse concentrated (VC) application at different times in relation to that of mineral fertilizer. Another objective is to determine the net N mineralization after VNC and VC addition to the soil. Two field experiments will be set up in which GHG will measured as a function of , time of vinasse and fertilizer application: both types of vinasse will be applied 30 days before and 30 days after mineral fertilization. Incubation experiments will be installed in order to determine the aerobic mineralization of both types of vinasse to the soil. GHG samples of N2O, CO2 and CH4 will be taken every two days for two months after fertilizer and vinasse application in the field; later, when GHGs emission rates become low, samplings will be done in longer time intervals (every 15 days), except when high emissions are expected (rain events), when samplings will be done again with short time intervals. The gas samples will be analysed by gas chromatography. The accumulated emission will be submit to ANOVA and means will be compared by orthogonal contrasts. The results of this research will contribute to a) better understanding of the factors that influence the flow of greenhouse gases, especially N2O; b) to determine better strategies for GHG emissions mitigation. Collaboration have been established with the scientists of the Department of Microbial Ecology of the Netherlands Institute of Ecology (NIIO),. who will use the same experiments to quantify microbial functional groups and the abundance of microbial genes in C and N cycles under different management practices from sugar cane in Brazil after the application of two types of vinasse combined with N fertilizer and straw.
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