Effect of crop residue incorporation on soil organic carbon and greenhouse gas emissions in European agricultural soils

Soil organic matter (SOM) improves soil physicochemical and biological properties, and the sequestration of carbon in SOM may mitigate climate change. Soil organic carbon (SOC) often decreases in intensive cropping systems. Incorporation of crop residues (CR) may be a sustainable management practice to maintain the SOC levels and to increase soil fertility. This study quantifies the effects of CR incorporation on SOC and greenhouse gas (GHG) emissions (CO2 and N2O) in Europe using data from long-term experiments. Response ratios (RRs) for SOC and GHG emissions were calculated between CR incorporation and removal. The influence of environmental zones (ENZs), clay content and experiment duration on the RRs was investigated. We also studied how RRs of SOC and crop yields were correlated. A total of 475 RRs were derived from 39 publications. The SOC increased by 7% following CR incorporation. In contrast, in a subsample of cases, CO2 emissions were six times and N2O emissions 12 times higher following CR incorporation. The ENZ had no significant influence on RRs. For SOC concentration, soils with a clay content >35% showed 8% higher RRs compared with soils with clay contents between 18 and 35%. As the experiment progressed, RR for SOC concentration increased. For N2O emissions, RR was significantly greater in experiments with a duration <5 yr compared with 11-20 yr. No significant correlations were found between RR for SOC concentration and yields, but differences between sites and study durations were detected. We suggest that a long duration of crop residue incorporation is a win-win scenario under a continental climate. We conclude that CR incorporation is important for maintaining SOC, but its influence on GHG emissions should be taken into account as well.