Soil carbon dynamics in integrated agricultural systems in Minas Gerais state, Brazil: A meta-analysis

The state of Minas Gerais, Brazil, has one of the highest rates of carbon dioxide emission in the country with a large part of these emissions attributed to extensive livestock on degraded pastures. Integrated agricultural production systems are considered a promising strategy to alleviate the negative impacts on soil caused by agriculture (e.g., soil carbon losses via CO₂ emissions) while keeping food production. However, the extent to which integrated systems [i.e., integrated crop-livestock (ICL) and integrated crop-livestock-forestry (ICLF)] can contribute to counterbalance soil organic carbon (SOC) losses is limited. Here, through a meta-analysis, we provide a regional-scale assessment of changes in SOC stocks associated with the adoption of ICL and ICLF systems in Minas Gerais state, Brazil. Additionally, we further investigated how SOC dynamics in these systems are affected by distinct soil (e.g., texture, depth) and climatic (e.g., temperature, precipitation) variables. Our results indicate that both ICL and ICLF systems resulted in SOC accrual after their implementation, at average rates of 1.09 and 1.21 Mg ha⁻¹ yr⁻¹, respectivelly. The age of the system affected SOC stocks only in the ICLF system, particularly between 4 and 8 years, in which SOC stocks increased at an average rate of 1.3 Mg ha⁻¹ yr⁻¹. While SOC stocks decreased in clay-sandy soils under ICLF systems, they increased in clay loam soils (1.06 Mg ha⁻¹ yr⁻¹). No clear trend was observed for ICL systems regarding soil texture. Positive effects of precipitation on SOC stocks in ICLF and ICL systems were observed only between 880 and 1000 and 1500–1700 mm, respectively. Clear effects of temperature on SOC stocks were observed only between 22 and 25 °C in ICLF systems. Soil depth had no significant effect on the rate of SOC stock change in the systems evaluated. Although the observed results help to better understand how integrated agricultural systems can affect SOC dynamics, the lack of detailed information in the studies used in our meta-analysis limits statically comparisons. However, our results indicate clear trends that ICLF and ICL systems can contribute to increasing SOC sequestration, and which climate and soil characteristics might be considered to maximize the efficiency of these systems in increasing SOC across Minas Gerais state, Brazil.