Total and Labile Organic Carbon in Integrated Systems and Managed Pastures in the Brazilian Cerrado

The quantification of carbon (C) in agricultural soils is of paramount importance for assessing the potential of management to maintain or improve soil health and reduce greenhouse gas emissions.  The study aimed to evaluate the levels and stocks of total and labile organic carbon (TOC and POXC) in agricultural production areas in the Brazilian Cerrado. The study was conducted on a farm in Unaí, Minas Gerais, Brazil. The areas evaluated were: managed pasture (PA; 7 years), integration crop-livestock (ICL; 4 years), and native Cerrado vegetation (NV). Soil samples were collected from the 0-5, 5-10, 10-20, and 20-30 cm layers. The TOC and POXC contents were determined by K₂Cr₂O₇ 0,167 mol L^-1 and KMnO₄ 0,02 mol L^-1, respectively. The accumulated stock (0-30 cm) (StTOC and StPOXC) was calculated. ANOVA and Tukey's test were performed at 5%. Differences in TOC content were found only in the 0-5 cm layer, with higher contents in the PA and NV areas (28,0 and 24,6 g kg⁻¹) compared to ICL (18,8 g kg⁻¹). The POXC, StTOC, and StPOXC values did not differ. However, when replacing NV with the management practices, an increase of 1,7 Mg of TOC ha⁻¹ year⁻¹ was observed in PA and a loss of 0,625 Mg of TOC ha⁻¹ year⁻¹ in ICL. It is concluded that PA was efficient in contributing and accumulating C in the surface soil layer, and the potential of CLI to store C has been confirmed over the years of adoption.