Dissolved organic matter (DOM) in soils play an essential role in soil physical, chemical and biological processes, but little information is available on the biodegradability of plant-derived DOM and its effect on soil carbon and nitrogen sequestration in field soils. The objectives of this study were to investigate the impacts of crop residue-derived DOM on soil CO 2 and N 2O emissions, as well as soil carbon and nitrogen sequestration by adding water extracts of maize stalk (i.e., plant-derived DOM) to soils. In this study, wheat was grown in pots under field conditions with treated soils, the soils treatments were: plant-derived DOM (PDOM), urea nitrogen (N), PDOM + urea nitrogen (PDOM + N), as well as a control with no additions to soil (CK). Adding plant-derived DOM to soil increased soil CO 2 and N 2O emissions ( P<0.05). During the wheat growing season, the cumulative CO 2-C emission from CK, PDOM, N and PDOM + N was 1071, 1577, 1362 and 1496 g C m -2, respectively. Meanwhile, the cumulative N 2O-N emission from CK, PDOM, N and PDOM + N was 1888, 2565, 23910 and 2587 mg N m -2, respectively. Compared with N treatment, DOM addition had little effect on soil N sequestration, but it accelerated the decomposition of native soil organic carbon (SOC) and caused a net loss of SOC. The soil C sequestration decreased about 15167 and 5145 g C m -2 in PDOM and PDOM + N treatments, respectively. The increased microbial biomass and root biomass were responsible for the greater CO 2 emission in DOM-amended soils. Negative correlation between dissolved organic carbon (DOC) content and N 2O flux suggested that the release of N 2O was dependent on the supply of DOC. These results indicated that the supply of plant-derived DOM exacerbated soil CO 2 and N 2O emissions and reduced soil C sequestration. Therefore, agricultural management practices that increase the stability of highly soluble C inputs and/or retard the decomposition of crop residues should be adopted to decrease soil greenhouse gas emission and increase soil C sequestration.
