联合施肥对复合污染农田水稻As、Cd吸收的影响

探究不同施肥模式与土壤调理剂联合措施对As-Cd复合污染农田水稻生长及水稻不同部位吸收转运重金属的影响，为中轻度复合污染农田的安全利用提供科学依据。在As-Cd复合污染农田上，分别设置农民常规施肥（尿素+过磷酸钙+氯化钾）、碱性复合肥料、水稻专用肥3种施肥模式以及分别与硅钙土壤调理剂联合配施的试验处理，测定了不同处理对水稻长势及产量水平、不同器官（根、茎、叶、籽粒） As、Cd的累积量，以及土壤重金属有效态、pH和有机质，重点分析了硅钙调理剂对水稻籽粒As、Cd含量及转运的影响因子和作用效应。结果表明：在As-Cd复合污染农田上，与对应单一化肥相比，仅碱性肥料与硅钙调理剂的联合施用下水稻的茎粗、穗长、穗粒数、产量4项指标分别提高了18.4%、7.8%、24.9%、16.1%，且均达到了显著差异（P<0.05），而常规施肥和水稻专用肥模式下的联合施肥对水稻包括产量在内的各农艺指标起到了部分抑制或无显著影响的效果；3种施肥模式下，以碱性肥料与硅钙调理剂的联合措施对水稻各器官中As、Cd的吸收累积抑制效果最好，其中对籽粒、叶片、茎秆、根系中As的累积抑制率分别为32.1%、19.8%、21.8%、32.7%，对籽粒、根系Cd的累积抑制率分别为43.8%、10.3%，且均达到了显著性差异水平（P<0.05）；碱性肥料+硅钙土壤调理剂联合措施在降低根系对土壤As、Cd吸收同时，对通过根系进入到茎秆的重金属As、Cd的再分配进行了调控，即促进了茎秆As、Cd向叶片转运，抑制了其向籽粒转运。3种联合施肥措施中，以碱性肥料+硅钙土壤调理剂对As-Cd复合污染农田安全利用的效果最佳，不仅降低了水稻（尤其是籽粒）对As、Cd的吸收转运，还提高了水稻的产量水平。

Effects of combined fertilization on the absorption of As and Cd in rice from polluted farmland

This study investigated the effects of the combined measures of different fertilization modes and soil conditioners on rice growth and the absorption and transportation of heavy metals in different parts of As-Cd compound-contaminated farmland, which helped to provide a scientific basis for the safe use of moderately and slightly contaminated farmland. In this study, three single chemical fertilizer application models were set up on the As-Cd compound-contaminated paddy field soil, including conventional fertilizer(urea + superphosphate+potassium chloride), alkaline compound fertilizers, and rice-specific fertilizers. Treatments with the combined application of a silicon-calcium soil conditioner were also conducted. The effects of different treatments on the rice growth and yield levels, the accumulation and transportation of As and Cd in different organs(including roots, stems, leaves, and grains), and the availability of soil heavy metals, pH, and organic matter were measured. The key influencing factors on the As and Cd contents of the rice grains under the combined fertilizer treatments were analyzed. The results showed that in the As-Cd compound-contaminated farmland, compared with the corresponding single fertilizer treatment, the combined application of only alkaline fertilizer and silicon-calcium conditioner improved the four indicators of rice stem diameter, spike length, seeds per spike, and yield by 18.4%, 7.8%, 24.9%, and 16.1%, respectively, which all showed significant differences(P<0.05), while the combined fertilization under the conventional fertilization and rice-specific fertilizer mode had a variety of agronomic growth indicators including partial suppression of the rice yield or no significant effect. Under the conditions of the three fertilization measures, combined fertilization under the mode of alkaline fertilizer had the best inhibitory effect on the absorption and accumulation of As and Cd in rice organs, among which the inhibition rates of As accumulation in the stems and roots reached 32.1%, 19.8%, 21.8%, and 32.7%, respectively, and the cumulative inhibition rates of Cd in the grains and roots reached 43.8% and 10.3%, respectively, with both reaching significant levels(P<0.05). The combined measures of alkaline fertilizer+silicon-calcium soil conditioner not only reduced the absorption of As and Cd in the soil by the roots, but also regulated the redistribution of As and Cd that entered the stem through the roots. In other words, the transport of As and Cd to the leaves was promoted, while the transport to the grains was inhibited. Among the three combined fertilization measures, the alkaline fertilizer+silicon-calcium soil conditioner showed the best application effect on the As-Cd compound-contaminated farmland, which not only reduced the absorption and transportation of As and Cd by the rice (especially the grains), but also promoted the rice agronomic growth indicators and yield.