Impact of Chinese milk vetch incorporation with reduced chemical fertilizers on the soil properties, rice growth and cadmium uptake in Cd-contaminated paddy fields

Green manure returning can improve soil fertility and crop production, and immobilize heavy metals in the soil. However, limited information is available on the effects of green manure replacing chemical fertilizers on soil properties and crop growth. In this study, we investigated the effects of Chinese milk vetch incorporation with reduced chemical fertilizers on soil properties, rice agronomic traits and cadmium (Cd) accumulation by field experiments, and four treatments were conducted: chemical fertilizer alone (CF), milk vetch alone (MV), milk vetch plus 80% chemical fertilizers (MVCF80), and milk vetch plus 50% chemical fertilizers (MVCF50). The results showed that all milk vetch treatments decreased soil pH and Eh, and increased the SOM, DOC contents and the activities of catalase and urease. The soil DTPA-Cd contents decreased by 20.41%, 18.20%, and 21.22%, and the Cd accumulation in rice root, stem, leaf, and grain decreased by 21.13%-37.62%, 20.74%-39.61%, and 21.91%-43.56% under MV, MVCF80, and MVCF50 treatments, respectively. Additionally, the MVCF80 treatment showed a better rice agronomic traits and grain yield than others. These data revealed the great potential of milk vetch incorporation with chemical fertilizer reduction in decreasing Cd accumulation in rice plants and improving rice quality and yield of Cd-contaminated paddy fields.