Impact of Pasture, Agriculture and Crop-Livestock Systems On Soil Carbon Sequestration In Brazilian Cerrado.

In Brazil, land use change, agriculture and livestock sectors are among the main sources of greenhouse gases (GHG). The aim of this study was to evaluate CO₂, N₂O and CH₄ fluxes under different land uses in Montividiu, Goiás State, Brazil, as well as soil C sequestration rates. Areas under native vegetation (NV), pastures (PA), crop succession (CS) and integrated crop-livestock systems (ICL) were evaluated since they represent typical land use in Cerrado biome. Soil was sampled in March 2007 and April 2009. GHG were sampled from April 2007 to March 2009. Conversion of NV to PA and CS resulted in C losses of 0,25 and 0,69 Mg ha^-1 year^-1, respectively. The implementation of ICL in agricultural areas acted as sink of C with accumulation rate of 0,66 Mg ha^-1 year^-1. However, in order to calculate soil C sequestration, it is necessary data not only on soil C stocks, but also N₂O and CH₄ fluxes. The N-N₂O fluxes converted into C-equivalent were -0,28, -0,10 and -0,28 and C-CH₄ fluxes -0,01, +0,01 and -0,01 Mg ha^-1 year^-1, respectively for PA, CS and ICL. Assuming that GHG fluxes obtained in 24 months represent the whole period after land use changes, it was possible to obtain soil C sequestration rates. The global balance of GHG, expressed in C equivalent, showed losses of 0,54 and 0,78 Mg of C ha^-1 year^-1, respectively, for the conversion of VN into PA and CS. The CS conversion to ICL resulted in soil C sequestration of 0,37 Mg of C ha^-1 year^-1. In this study, soil acted as a source of GHG to atmosphere in the conversion of NV to PA and CS. On the other hand, the adoption of ICL systems resulted in soil C sequestration and GHG emissions mitigation in agricultural areas.