Conservation agriculture based on diversified and high-performance production system leads to soil carbon sequestration in subtropical environments

Soils can be a source or sink of atmospheric CO2, depending on the historic and existing land use and management. We used long term soil management database of a production farm that is based on principles of conservation agriculture such as: a) eliminate soil disturbance; b) maintain permanent soil surface cover; C) adopt crop diversity with high biomass-C input; for 30 years and agroecosystem models to study the potential of different management options to sequester C in soils. Using Century and Roth-C models we simulated the carbon stocks evolution in the farm and four subtropical soil management scenarios and studied C sequestration potential. The scenarios were: a) existing farm biomass input (14.5 Mg ha−1 year−1) or C input (6.5 Mg ha−1 year−1); b) 15% increase of farm biomass input (16.7 Mg ha−1 year−1) or C input (7.5 Mg ha−1 year−1); c) 15% decrease of farm biomass (12.3 Mg ha−1 year−1) or C input (5.5 Mg ha−1 year−1) and, d) 30% decrease of farm biomass input (10.1 Mg ha−1 year−1) or C input (4.5 Mg ha−1 year−1). Our results demonstrate that soil organic carbon continuously increased after conservation management practices adoption in 1985 until 2015, and currently soil organic carbon is in equilibrium. We found that an increase of 2.2 Mg ha−1 year−1 biomass-C input for 60 years resulted into increase of 12 Mg ha−1 soil organic carbon stocks. The same way, crop yields increased with time, and were more pronounced for maize compared to soybean and wheat. The scaling up of model results to similar climate and soil types indicated that conservation management practices has the potential to sequester 2.7 ± 0.02 Pg C at 0–20 cm and 4.8 ± 3 Pg C at 0–100 cm soil depth in 43 million ha area globally. In the 30% and 15% decrease scenarios the sequestration were 2.2 ± 0.02 and 2.4 ± 0.02 Pg C at 0–20 cm an in 15% increase scenario it goes to 3.2 ± 0.02 Pg C. This equilibrium soil organic carbon stocks considering the currently adopted system are equivalent to 3.5–4.5% of the world SOC stocks in 3% of the world croplands and correspond to 6 years of global land use and land use change emissions, indicating that conservation management practices can lead the soil be a sink and a promising tool to promote C sequestration in subtropical soils.