Flux Of N2o By Soil Under Silvipastural System.

The emission of greenhouse gases by agricultural activity has been focused worldwide. In view of this, the knowledge about systems that mitigate these gases is of vital importance. The objective of this research is to evaluate the N₂O flux by soil of massai grass pastures in silvipastural system kept under intermittent stocking by sheep. The experiment was conducted in forage science sector of FCAV, Jaboticabal UNESP, Brazil, from January to March 2013. The treatments consisted of two eucalyptus spacings (6.0 X 2.0m and 12.0 X 2.0m) subjected to grazing, a treeless treatment also subjected to grazing and a treeless treatment that has not been grazed. For entry the criteria used was 95% of light interception and for exit the parameter was 15 cm of canopy height. Three cycles were performed and after grazing the pickets were fertilized with 50 kg / ha of nitrogen, being that only the treatment that had not been grazed received no fertilizer. N₂O flux, temperature and soil moisture were evaluated after the removal of the animals from pickets for 10 days. The average cumulative emission of the three grazing cycles in 10-day evaluation of N₂O was 1476.1 (± 730.7), 2682.6 (± 1642.3) and 2156.648 (± 1077.4) μgN-N₂O for the grazed treatments with spacing of 6 and 12 m, and the treatment without trees, respectively. For the treatment without trees and ungrazed was observed a cumulative N₂O consumption of 622.6 (± 572.4) μgN-N₂O. In the third grazing cycle the N₂O emission increased by 80, 77 and 74% in relation to the other cycles in grazed treatments spacing 6 and 12 m and treeless. In the treatment without trees and without grazing the consumption of N₂O increased by 65% in the third cycle. The introduction of animals in the silvipastural system alter the flux of N₂O.