Wang Yun, Liang Hai, Li Shun, Zhang Zihan, Liao Yulin, Lu Yanhong, Zhou Guopeng, Gao Songjuan, Nie Jun, Cao Weidong
College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing 210095, Jiangsu, China.
Soil and Fertilizer Institute of Hunan Province, Hunan Academy of Agricultural Sciences, Changsha 410125, Hunan, China.
Sci Total Environ. 2022 Feb 1;806(Pt 2):150622. doi: 10.1016/j.scitotenv.2021.150622. Epub 2021 Sep 28.
The danger posed by cadmium (Cd) pollution to rice production is continuously increasing. Co-utilizing milk vetch (Astragalus sinicus L.) and rice straw is a good practice for rice yield and soil fertility in south China. However, its effects on Cd availability in soil-rice systems remain unclear. A micro-plot trial of two typical paddy soils (alluvial sandy soil and reddish clayey soil) in south China was conducted to investigate the effects of milk vetch, rice straw, lime, and their combined application on Cd availability and the related mechanisms. Soil chemical properties, CaCl-extractable Cd (CaCl-Cd), total content of Cd (Total-Cd), Cd fractionation (BCR sequential-extraction method), and Cd accumulation in rice were measured. Results showed that the co-utilization of milk vetch, rice straw, and lime (GRFL) decreased the Cd content in rice grain by 91.43% and 15.63% in early rice of two soils, respectively. Cd was not detected in late rice grains. CaCl-Cd decreased by 0.025 mg kg in late rice of alluvial sandy soil, 0.057 and 0.044 mg kg decreased in early and late rice of reddish clayey soil, and Total-Cd decreased by 19.4% and 9.1% for early rice of two soils, respectively. Co-utilizing milk vetch, rice straw, and lime changed the distribution of different chemical forms of Cd, decreased the content of bioavailable Cd in soil by reducing the Aci-Cd and RedCd, and benefited the formation of more stable residual fraction (ResCd). Redundancy analysis showed that the improvement in soil pH, dissolved organic matter (DOM), and other soil properties was the main cause of the transformation of Cd form. Among the soil properties, pH and DOM had the greatest impacts on Cd availability. In conclusion, co-utilizing milk vetch and rice straw can alleviate the danger of soil Cd in rice production, and this effect could be strengthened by applying lime.
镉（Cd）污染对水稻生产构成的威胁日益增大。在中国南方，紫云英与稻草共同利用是实现水稻高产和土壤肥力提升的良好做法。然而，其对土壤-水稻系统中镉有效性的影响仍不明确。在中国南方开展了针对两种典型水稻土（冲积砂质土和红色黏土）的小区试验，以研究紫云英、稻草、石灰及其组合施用对镉有效性及相关机制的影响。测定了土壤化学性质、氯化钙提取态镉（CaCl-Cd）、镉总量（Total-Cd）、镉形态分级（BCR连续提取法）以及水稻中的镉积累量。结果表明，紫云英、稻草和石灰共同利用（GRFL）使两种土壤早稻的稻谷镉含量分别降低了91.43%和15.63%。晚稻籽粒中未检测到镉。冲积砂质土晚稻的CaCl-Cd降低了0.025 mg/kg，红色黏土早稻和晚稻的CaCl-Cd分别降低了0.057和0.044 mg/kg，两种土壤早稻的Total-Cd分别降低了19.4%和9.1%。紫云英、稻草和石灰共同利用改变了镉不同化学形态的分布，通过降低酸溶态镉（Aci-Cd）和可还原态镉（RedCd）减少了土壤中生物可利用镉的含量，有利于形成更稳定的残渣态镉（ResCd）。冗余分析表明，土壤pH值、溶解性有机质（DOM）等土壤性质的改善是镉形态转化的主要原因。在土壤性质中，pH值和DOM对镉有效性的影响最大。综上所述，紫云英与稻草共同利用可减轻水稻生产中土壤镉的危害，施用石灰可强化这种效果。
