Impact of long-term no-tillage and cropping system management on soil organic carbon in an Oxisol: A model for sustainability

Soil organic carbon (SOC) was assessed in a long-term (19 yr) experiment comparing conventional tillage (CT) and no-tillage (NT) management systems and various winter cover crop treatments in a Rhodic Hapludox in southern Brazil. After 19 yr, NT resulted in 6.84 Mg C ha(-1), in the upper soil layer (0-10 cm), which represented 64.6% more than CT. In the 0 to 20 cm soil layer, the NT system sequestered 1.24 Mg C ha(-1) yr(-1), while CT sequestered 0.96 Mg C ha(-1) yr(-1). Independent of soil management, the fallow treatment resulted in the lowest SOC stocks to the 40-cm soil depth compared to all other winter treatments. We compared SOC levels of the experimental site with a nearby-forested area, which has never been cleared. No-till management combined with winter cover crops resulted in soil properties that most closely resembled the undisturbed forest. Maize grain yields and soybean seed yields were 6 and 5% higher, respectively, under NT than CT. Our results point to NT management combined with winter cover crops as the management system of choice to achieve sustainable crop production on Oxisols in the subtropical and tropical regions of the world.