Intensification and diversification of pasturelands in Brazil: Patterns and driving factors in the soil carbon stocks

The extensive system of pasture management in Brazil can reduce soil C stocks and increase CO2 emissions to the atmosphere. However, the adoption of sustainable management systems can change these conditions and enact modern practices of natural resource management as defined by the concept of ecosystem services. A field study was therefore carried out to assess the effects of adopting more intensive and diversified systems of pasture management on the quality and stocks of soil C. Treatments included fertilized pasture (FP), integrated crop -livestock (ICL), and integrated livestock-forest (ILF) and were compared to conventional management systems (CS) under different soil and climate conditions (tropical humid, subtropical dry and subtropical humid). Soil carbon stocks and soil organic matter (SOM) fractions were determined in the top one-meter layer. With the SOM fractions, we calculated the C lability (LI), pool (CPI) and management (CMI) indices. The results showed that adopting ICL systems under the conditions of a tropical humid and subtropical humid climate produced increases in soil C stocks of 0.75 Mg ha-1 yr- 1 (P < 0.01) and 0.15 Mg ha-1 yr- 1 (P < 0.05), respectively, relative to the CS. Similarly, the conversion of a CS to FP (tropical humid climate) and ILF (subtropical dry climate) led to increases in soil C stocks of 2 and 0.55 Mg ha-1 yr- 1 (P < 0.05), respectively. In general, the adoption of more intensive and diversified systems of pasture management can also afford increases in the LI, CPI and CMI indices. These results can serve as a scientific basis for government initiatives that focus on recovering degraded pastures in Brazil through the use of more sustainable management systems and can also help to sequester more C in soils.