Soil N2O fluxes in integrated production systems, continuous pasture and Cerrado

The objective of this study was to evaluate N2O fluxes from integrated crop-livestock (ICL) and integrated crop-livestock forest (ICLF) systems, continuous pasture and native Cerrado. The experiment was conducted at Embrapa Cerrados, Planaltina-DF, in a Red Oxisol, between February 2012 and April 2014, following the transition of crop to livestock, which began in March 2012, with the sowing of Brachiaria brizantha cv. Piat, intercropped with sorghum. The experimental design was a randomized block with three replications. The treatments were: cultivated area intercropped with rows of Eucalyptus, spaced 2 x 2 m between plants and 22 m between rows (ICLF); and an area cultivated without tree species (ICL), and also two adjacent reference areas: native Cerrado and continuous pasture. N2O productions were characterized by fluxes below 20 mu g N m(-2) h(-1). The ICL system had the highest cumulative flux with 2.84 kg N ha(-1), while the ICLF system obtained cumulative fluxes of 2.05 kg N ha(-1). The native Cerrado showed a negative balance, with -0.05 kg N ha(-1). The dry season was mostly characterized by low N2O fluxes ranging between 10 mu g N m(-2) h(-1) and negative values, whereas higher N2O fluxes were observed after precipitation events, especially those following a long drought period. The water filled pore space was the factor that best explained N2O fluxes, but higher fluxes were observed after the application of nitrogen fertilizer. There was a positive correlation between microbial biomass carbon and N2O fluxes in the ICL and ICLF systems.