Leguminous forage introduction and returning reduced soil inorganic carbon loss on the Loess Plateau

Abstract

Despite evidence from experiments that no-till and stubble retention promote soil organic carbon accumulation, it is not yet clear if this is the case for soil inorganic carbon (SIC), particularly in the arid and semiarid Loess Plateau. Based on field observations from 2001 to 2020, we methodically characterized the spatial–temporal dynamics of SIC and driving factors in a forage-crop rotation system. The results showed that 19 years continuous application of no-till or stubble retention practices resulted in SIC loss at the 0–10 cm soil depth at rates of 0.01–0.07 g kg−1 yr−1, the introduction of leguminous forages reduced the loss rate. The effects on SIC were greater at the 60–500 cm soil depth than at the 0–60 cm soil depth, SIC accumulated significantly in the deeper layer, and leaching and re-precipitation mainly occurred in the 60–200 cm layer. When performed on average over the 0–500 cm soil profile, no-till and stubble retention increased the SIC storage by 1.87–4.78 t ha−1 after maize harvest, while reduced by 1.04–1.20 t ha−1 after vetch harvest. The effects on SIC were mainly influenced by soil organic carbon according to the structural equation model. We concluded that leguminous forage introduction and returning to the field reduced the SIC loss in the rotation systems. The results highlight the importance of better understanding SIC dynamics when predicting the soil carbon budget.