Planting milk vetch (Astragalus sinicus L.) is an effective practice to enhance rice yield and soil fertility in southern China. The arable land resources in China are scarce, while farmland soil degradation is becoming more serious, so that it is important to find a way to simultaneously carry out ecological restoration and improve farmland soil fertility. The green manure research group of the Innovation Team of Fertilizer and Fertilization Technology of the Institute of Agricultural Resources and Regional Planning (IARRP), CAAS, has proposed a new scientific hypothesis of utilizing green manure to slow down and prevent farmland soil degradation, and has carried out exploratory research on the unique effects of green manure on Cadmium (Cd) pollution in paddy fields and control of excessive Cd content in rice grain.

In this work, a micro-plot trial was started in 2015 in two typical paddy soils (alluvial sandy soil and reddish clayey soil) in Central China's Hunan province to investigate the effects of different green manure utilization measures on Cd availability and related mechanisms.

Results showed that the co-utilization of milk vetch, rice straw, and lime prevented the absorption of Cd by rice and decreased Cd content in rice grain. The mixed use of milk vetch, rice straw, and lime has changed the distribution of different chemical forms of Cd, decreased the content of bioavailable Cd in soil by reducing the Aci-Cd and Red-Cd, and benefited formation of more stable residual fraction (Res-Cd), thus reducing the Cd accumulation in rice grain.

The findings were published in the international top academic journal Science of the Total Environment (IF 7.963). Under the guidance of research fellow Cao Weidong from the IARRP, CAAS, Wang Yun, a postgraduate student at the College of Resources and Environmental Sciences of Nanjing Agricultural University, is the first author. Cao Weidong, Dr. Gao Songjuan from Nanjing Agricultural University, and research fellow Nie Jun from the Hunan Soil and Fertilizer Institute are co-corresponding authors. The research was funded by the China Agriculture Research System - Green Manure (CARS-22) of the Ministry of Finance and the Ministry of Agriculture and Rural Affairs, and the Fundamental Research Funds for Central Universities (KJQN202118).

https://doi.org/10.1016/j.scitotenv.2021.150622

Y. Wang, H. Liang, S. Li, et al., Co-utilizing milk vetch, rice straw, and lime reduces the Cd accumulation of rice grain in two paddy soils in south China, Science of the Total Environment (2021)