连续施硅对双季稻镉硅累积效应的影响

为研究硅肥对土壤镉生物有效性以及双季稻对镉硅积累的影响，在稻田土壤镉较高［ω（总Cd）为1.03 mg·kg^-1］污染条件下，开展双季稻连续基施硅肥180 kg·hm^-2（以SiO₂计）的田间定位试验.结果表明，双季稻田连续施用硅肥能够增加土壤有效硅含量，增幅为108.1%~275.0%，同时提高土壤1.15~1.33个pH单位，施用硅肥早、晚稻土壤DTPA-Cd含量降幅分别为12.3%和15.9%，差异达显著水平；施硅促进了土壤镉向稳定形态的转化，土壤可交换态EXC-Cd含量降幅为2.6%~5.1%，QW处理降低达显著水平；施硅肥处理，碳酸盐结合态CAR-Cd含量降低，降幅为8.6%~24.9%，显著增加了铁锰氧化态FMO-Cd含量，增加了土壤有机结合态OR-Cd含量，增幅为2.3%~12.8%，残渣态RES-Cd含量增幅为2.3%~6.0%；连续施硅肥降低了水稻对镉的积累，早稻根、茎叶和稻米平均降幅分别为38.4%、49.7%和50.9%，晚稻根、茎叶和稻米平均降幅分别为30.6%、34.4%和39.2%；硅处理显著降低了水稻根吸收系数（AF_土/根），降幅为25.5%~49.6%，同时降低了水稻根向茎叶的转运系数（T_根/茎叶），降幅为13.5%~52.6%，差异显著，早、晚稻稻米镉富集系数（BAF）分别平均降低6.0%和8.0%，其中粉末状硅肥对降低水稻镉吸收效果最佳.综上表明硅肥能够降低水稻对镉的吸收积累，然而硅肥持续性降镉效应不明显.

Impacts of Uptake and Accumulation of Cd on Double Rice-Paddy Soil by Silicon Fertilizer Continuous Application

The impacts of silicon (Si) fertilizers on cadmium (Cd) bioavailability in soil and Cd accumulation in paddy-rice plants were investigated in a field positioning test. The results indicated that the continuous application of 180 kg·hm^-2 Si fertilizers improved soil bioavailable Si in paddy-rice fields by 108.1%-275.0% and improved pH values by 1.15-1.33 in soil. The difference in the contents of DTPA-Cd in soil by 12.3% and 15.9% was significant in early and late rice, respectively. The continuous application of silicon promoted the transformation of soil cadmium to a stable form and reduced the contents of exchangeable Cd and carbonate binding state Cd in the soil by 2.6%-5.1% and 8.6%-24.9%. The contents of ferric manganese oxide binding state Cd were increased significantly; meanwhile, the contents of organic binding state Cd and residue state Cd in soil were improved by 2.3%-12.8% and 2.3%-6.0%, respectively. The contents of Cd in the root, shoot, and rice were reduced by 38.4%, 49.7%, and 50.9% in early season rice and by 30.6%, 34.4%, and 39.2% in late season rice, respectively. The absorption factors and translocation factors were reduced significantly by 25.5%-49.6% and 13.5%-52.6%, and the average bioaccumulation factors were decreased by 6.0% and 8.0% in early and late season rice. The powder Si fertilizer had the best results overall. In conclusion, Si fertilizer could reduce the absorption and accumulation in rice; however, the continuous Cd reduction effect of continuous application Si fertilizer was not obvious.