Evaluating the contributions of earthworms to soil organic carbon decomposition under different tillage practices combined with straw additions

The incorporation of earthworms and straw into cropland soil can greatly affect soil structure and soil organic C (SOC) dynamics. However, information regarding how earthworms affect both carbon (C) in its transition from residue into soil and SOC turnover under conventional tillage (CT) and conservation tillage is limited, and some results are even contradictory. Moreover, most of studies were conducted out based on sieved soil samples. In this study, intact soil samples were used to analyze the effects of earthworms (Eisenia foetida) and both of earthworms and straw addition on SOC fractions and soil CO2 emission in a 30-day incubation experiment with CT and no tillage (NT) treatments. The results showed that CT accelerated the straw decomposition and increased the content of soil active C. In contrast, NT resulted in slower decomposition of the original straw and reduction of the total amount of SOC and soil active C. The earthworms could inhibit the straw from decomposing in CT and stimulate the decomposition of straw in NT. Whatever in NT or CT, earthworms did not affect soil CO2 emission, but straw addition significantly increased soil CO2 emission. The results of this study provide the selection of the appropriate tillage practice as well as the amount of returned straw to fertilize the soil.