Integrated farming systems for improving soil carbon balance in the southern Amazon of Brazil

Integrated farming systems (IS) are one of the main strategies of the Brazilian government to reduce or compensate for carbon emissions from agriculture with simultaneous improvement in production efficiency. The IS are agricultural production systems that combine crop, livestock and forestry activities in the same area. The aim of this study was to address soil organic carbon (SOC) stocks under two agriculture areas with IS, in comparison with one exclusively used as low-input pasture (Pasture). The IS consisted of growing forestry species (Eucalyptus urograndis) simultaneously with soybean (Glycine max) and aerobic rice (Oryza sativa) for 2 years when grain crops were followed by palisade grass (Urochloa bryzantha). The study was carried out in real farm conditions in the southern Amazon ecosystem, north of Mato Grosso State, Brazil. SOC stocks were measured to 1 m soil depth. Compared to Pasture, areas of higher SOC stocks were identified in IS under the tree lines below 0.3 m, where there was no soil N deficiency. Our results indicated that, under the local edaphic and climatic conditions of the study, IS with trees can promote SOC accumulation even in a short term, such as 3 years in this case study, if soil fertility constraints do not exist.