3种有机物料对土壤镉有效性及水稻镉吸收转运的影响

种植绿肥、秸秆还田和施用有机肥是稻田土壤有机质提升的主要途径，明确其对土壤镉（Cd）有效性及水稻吸收积累Cd的影响，对于我国南方Cd污染稻田的安全利用具有重要指导意义。采用田间小区试验，设置等量（2 250 kg·hm^-2，干质量）紫云英、油菜秆和有机肥施用处理，通过测定二乙烯三胺五乙酸提取态Cd （DTPA-Cd）、根表铁膜Cd含量和水稻各部位Cd含量，结合土壤理化指标和酶活性变化，对比分析3种有机物料对Cd在土壤-水稻系统迁移转运的影响并探讨其机理。结果表明： 3种有机物料提高了土壤溶解性有机碳（DOC）、有机质含量和水稻产量，增强了土壤过氧化氢酶和纤维素酶活性，在一定程度上增加了根表铁膜量及其Cd吸附量。与CK相比，紫云英、油菜秆和有机肥处理水稻根对Cd的吸收分别增加4.22%、16.99%和38.27%（P<0.05），Cd由水稻根向稻谷的转运系数和叶向稻谷的转运系数均明显提高，水稻稻谷Cd含量分别显著增加32.67%、39.60%和54.46%（P<0.05）。在Cd污染土壤上施用有机物料虽能提升土壤肥力，但会促进水稻根系对Cd的吸收和向稻谷的转运。因此在南方Cd污染稻田应谨慎施用有机物料，防止由此导致的稻米Cd积累风险。

Effects of three organic materials on the availability of cadmium in soil and cadmium accumulation and translocation in rice plants

Planting green manure, returning crop straw, and applying organic manure are the main methods for improving the soil organic matter in paddy fields. Clarification of their effects on soil Cd availability and the accumulation and translocation of Cd in rice may be useful for the safe utilization of Cd-contaminated paddy fields in south China. A plot field experiment with the application of equal amounts (2 250 kg·hm^-2; dry weight)of milk vetch, rape stalk, and organic fertilizer was conducted to measure the diethylenetriamine pentaacetic acid-extractable Cd, measure the Cd concentrations in iron plaque on roots and rice tissue, study the changes in the soil physical and chemical indexes and enzyme activities, and comparatively analyze the effects and the mechanisms of these three organic materials on the transport of Cd in soil-rice systems. The concentrations of dissolved organic carbon and organic matter in the soil and the yield of rice grains increased after applying these three types of organic materials. The activities of soil catalase and cellulase were also increased by applying organic materials. The concentrations of Fe, Mn, and Cd in iron plaque on the rice roots increased with the application of milk vetch, rape stalk, and organic fertilizer. Compared with that in the control, the Cd concentrations in the rice roots increased by 4.22%, 16.99%, and 38.27%(P<0.05)with the application of milk vetch, rape stalk, and organic fertilizer, respectively. The transport coefficients of Cd from root to grain and from leaf to grain significantly increased. Furthermore, the concentrations of Cd in the rice grains significantly increased by 32.67%, 39.60%, and 54.46% with the application of milk vetch, rape stalk, and organic fertilizer, respectively. In conclusion, the application of organic materials can enhance the absorption of Cd by rice roots and the accumulation of Cd in grains; therefore, organic materials should be carefully applied to Cd-contaminated paddy soil in south China in order to prevent the risk of Cd accumulation in rice.