Assessing strategies to enhance soil carbon sequestration with the DSSAT‐CENTURY model

The adoption of no-till (NT) has been proposed to recover soil organic carbon (SOC), which will aid the mitigation of climate change. However, studies have questioned the potential of NT soils to deliver SOC sequestration and sustain crop yields. No-till experiments are relatively recent (<50 years) and very few studies were able to assess SOC dynamics in high-yield agroecosystems. We used the DSSAT-CENTURY model to predict long-term SOC (0-30 cm) using datasets from two experiments assessing tillage and nitrogen (N) sources in a Mollisol from the midwest United States (28 years) and tillage and crop rotations in an Oxisol from southern Brazil (33 years). The conversion of prairie and grassland soils to conventional agriculture decreased SOC by 61 and 12% in the Mollisol and Oxisol, respectively. Soil organic C accrual in NT soils was >0.5 Mg C ha(-1) year(-1) under medium-low-yield maize in the Mollisol and negligible in the Oxisol under soybean/wheat rotation. Organic fertilization and crop rotation increased SOC accrual at both sites. Simulated SOC had good agreement with observations for NT soils but overestimated SOC in tilled soils. The model's parameters were then modified for tilled soils. Long-term simulations (100 years) revealed that SOC accrual in NT soils (0-15 cm) is partially offset by losses at 15-30 cm under low C inputs. Simulations with best crop management practices (BP; irrigation, high-yield cultivars, higher plant density and improved N fertilization) augmented C inputs and SOC stocks, ultimately recovering SOC to the levels of prairie soils. Our results suggest that the adoption of NT, recycling of organic fertilizers and the use of BP should be further promoted for recovery and permanence of SOC in agricultural soils.HighlightsStudies have questioned the potential of conservation agriculture (CA) to deliver SOC sequestration and sustain crop yields.We used the DSSAT-CENTURY model to simulate SOC dynamics in temperate and subtropical soils.No-till under moderate C/N inputs recovered topsoil SOC, but subsurface losses offset SOC accrual.Use of CA, organic amendments and best practice crop management (BP) is crucial for long-term SOC storage and permanence.