Crop residue-derived dissolved organic matter accelerates the decomposition of native soil organic carbon in a temperate agricultural ecosystem

Crop residue-derived dissolved organic matter (DOM) plays an important role in soil carbon (C) cycling. To investigate the effects of maize residue-derived DOM and urea additions on the native soil organic carbon (SOC) decomposition and soil net C balance a pot experiment was carried out during the winter wheat growing season in the North China Plain (NCP). The results showed that adding maize residue-derived DOM alone (RDOM) or together with urea (RDOM + N) accelerated the decomposition of native SOC and resulted in a net SOC loss. The net loss of SOC was 3.90 ± 0.61 and 3.53 ± 0.48 g C m −2 in RDOM and RDOM + N treatments, respectively. The stimulatory effect of per unit DOM-C addition on the native SOC decomposition was 0.25 ± 0.05 and 0.45 ± 0.07 for the RDOM and RDOM + N treatments, respectively. Increases in the microbial biomass and the activity of β-glucosidase, invertase and cellobiohydrolase as well as soil mineral N content were responsible for a more intense priming effect in DOM-amended soils. The positive relationship between primed soil C and soil available N ( R  = 0.76, P  < 0.05) suggested that the stimulation of decomposition of native SOC by DOM addition would be enhanced by nitrogen fertilizer application.