Carbon depletion by plowing and its restoration by no-till cropping systems in oxisols of subtropical and tropical agro-ecoregions in Brazil

The continuous use of plowing for grain production has been the principal cause of soil degradation. This project was formulated on the hypothesis that the intensification of cropping systems by increasing biomass-C input and its biodiversity under no-till (NT) drives soil restoration of degraded agro-ecosystem. The present study conducted at subtropical [Ponta Grossa (PG) site] and tropical regions [Lucas do Rio Verde, MT (LRV) site] in Brazil aimed to (i) assess the impact of the continuous plow-based conventional tillage (CT) on soil organic carbon (SOC) stock vis-à-vis native vegetation (NV) as baseline; (ii) compare SOC balance among CT, NT cropping systems, and NV; and (iii) evaluate the redistribution of SOC stock in soil profile in relation to soil resilience. The continuous CT decreased the SOC stock by 0_58 and 0_67MgCha_1 y_1 in the 0- to 20-cm depth at the PG and LRV sites, respectively, and the rate of SOC sequestration was 0_59 for the PG site and ranged from 0_48 to 1_30MgCha_1 y_1 for the LRV site. The fraction of C input by crop residues converted into SOC stock was ~14_2%at the PGsite and ~20_5% at the LRV site. The SOC resilience index ranged from 0_29 to 0_79, and it increased with the increase in the C input among the NT systems and the SOC sequestration rates at the LRV site. These data support the hypothesis that NT cropping systems with high C input have a large potential to reverse the process of soil degradation and SOC decline.