Dissolved organic carbon in cropland soils: A global meta-analysis of management effects

Dissolved organic carbon (DOC) in agricultural soils is a pivotal indicator of soil carbon response to management practices, facilitating substance transport, energy transfer, and information exchange. Despite its importance, there is limited understanding of the global impact of these practices on the magnitude, drivers, and functionality of soil DOC. Here, we conducted a meta-analysis of 3539 paired DOC, 196 paired soil carbon dioxide (CO₂) emissions, and 1424 paired crop yields from cropland soils to fill this knowledge gap. Management practices included conservation tillage (CT), nitrogen fertilizer, straw, manure, nitrogen combined with straw (NS), nitrogen combined with manure (NM), and biochar. DOC under NM, manure, NS, straw, nitrogen fertilizer, biochar, and CT increased significantly by 78.21%, 49.91%, 41.02%, 25.68%, 18.4%, 14.89%, and 9.74%, respectively. Except for biochar and CT, the other management practices also led to an increase in the DOC/SOC ratio, ranging from 7.66% to 15.79%. Biochar application decreases the DOC/SOC ratio by 25.02%, indicating its soil carbon stability and the potential for carbon sequestration. The intensity and duration of management practices emerged as driving factors influencing the DOC. Each unit increase of DOC under nitrogen fertilizer, straw, and NM not only effectively decreased the effect size of CO₂ emissions, but also increased the effect size of crop yields in contrast to CT, manure, NS, and biochar. Overall, this study highlighted the importance of the intensity and duration of management practices on DOC. The regulation of DOC through management practices is also required to account for both environmental aspects and crop yields for sustainable agricultural development.