Soil organic carbon sequestration efficiency with biochar addition across the croplands of China: A perspective from particulate and mineral-associated organic carbon.

Soil organic carbon (SOC) is typically fractionated into particulate and mineral-associated organic carbon (POC and MAOC). Biochar has been widely deployed to improve soil fertility, crop yield, and carbon sequestration. Organic carbon sequestration efficiency (OCse) is defined as an indicator that evaluates the capacity to convert exogenous organic carbon into SOC pools. However, the OCse in POC, MAOC, and SOC with biochar addition remains largely unquantified at a national scale. Here, a dataset was compiled to assess, explain, and predict the OCse in POC, MAOC, and SOC with biochar addition across the croplands of China. Biochar addition had positive influences on the OCse in POC, MAOC, and SOC. Moreover, the OCse was greater in POC than in MAOC. Multiple factors controlled the OCse in POC, MAOC, and SOC with biochar addition, including climate conditions, soil properties, experimental practices, and agronomic managements. High-resolution maps of OCse for POC, MAOC, and SOC were robustly generated through a machine learning algorithm in the topsoil of croplands across China. National-scale OCse in POC, MAOC, and SOC showed means and ranges of 81.2 % (8.5 %-443.0 %), 64.1 % (-12.4 %-424.4 %), and 136.4 % (17.8 %-791.3 %), respectively. Spatial heterogeneity in the OCse for POC, MAOC, and SOC was exhibited across geographic region, climatic zone, soil texture, land type, and cropping intensity. Specifically, high OCse in POC, MAOC, and SOC occurred in southern region, temperate-tropical climate, clay-textured soil, paddy field, and moderate cropping intensity. Collectively, our study reveals mechanistic insight into soil carbon sequestration and provides valuable guidance for sustainable biochar management.