Emissões de N2O e atributos microbiológicos do solo em integração lavoura-pecuária-floresta

The objective of this study was to evaluate the microbial biomass and N2O emissions from pasture in Crop-Livestock Integration (iLP) and Crop-Livestock-Forest Integration (iLPF), in addiction to native Cerrado and low productivity pasture. The experiment was conducted at Embrapa Cerrado, Planaltina-DF, in Red Latosol. The experiment was conducted in the period from February 2012 to April 2014, following the transition to livestock from crop, which began in March 2012, with the sowing of B. brizantha cv. Piatã, intercropped with sorghum, and the grass remaining throughout the experiment. The experimental design was a randomized block with three replications. The treatments were: cultivated area interspersed with rows of Eucalyptus urograndis, spaced 2 x 2 m between plants and 22 m between rows; and area cultivated in full sun, with no presence of tree species, in addition to controls: a native Cerrado and a low productivity pasture. Soil samples for the assessment of microbial biomass (0-10, 10-20 and 20-30 cm) were collected in February 2012 and February 2014 (rainy season) and July 2012 and September 2013 (dry season). The emission of N2O was evaluated using closed static chambers. The iLPF system did not promote change in NBM, Corg and total nitrogen contents in comparison to the iLP, but decreased the levels of CBM, basal respiration and qMic. The native Cerrado had higher levels of all evaluated factors, except total nitrogen, which showed no difference. N2O emissions were characterized by flow below 20 μg N m -2 h -1 , with approximately 20% of the data collected showing negative values. The iLP system had the highest cumulative emission with 2,86 kg N ha -1 , while the iLPF system and the low productivity pasture obtained emissions 2,05 kg N ha -1 and 0,41 kg N ha -1 , respectively. The native Cerrado showed a negative balance, with -0,05 g N ha -1 . The EPSA was the factor that best explained N2O emissions, but the biggest flows were observed after application of nitrogen fertilizer.