氯基和硫基肥对土壤镉水稻生物有效性的影响

为探明氯基和硫基化肥单施或混施对土壤镉（Cd）水稻生物有效性的影响，选取典型水稻土红黄泥（第四纪红色黏土母质发育），按不同比例添加氯基肥（KCl、NH₄Cl）和硫基肥［K₂SO₄、（NH₄）₂SO₄］，在3种外源Cd水平下（0、0.5和2.0 mg ·kg^-1）进行水稻盆栽试验，研究土壤pH、Cd形态、水稻植株各部位和糙米Cd富集情况.结果表明，施用氯基和硫基肥均会使土壤酸化，但氯基肥的影响更显著.水稻灌浆期，单施氯基肥较单施硫基肥的土壤pH值平均降低了0.28；水稻成熟期，氯基肥对残渣态Cd具有活化作用，而硫基肥会将酸可提取态Cd钝化为残渣态；氯基和硫基肥混施较单施同种肥料更易促进水稻植株富集Cd；糙米Cd富集量在氯基和硫基肥1 ：1处理时最高，为0.21 mg ·kg^-1（2.0 mg ·kg^-1外源Cd水平），较单施氯基肥提高了16.4%，较单施硫基肥显著提高了113.3%.因此，氯基肥和硫基肥混施会使水稻糙米Cd富集量上升，为保障粮食品质安全，水稻种植更宜单施硫基肥.

Effects of Chlorine-based and Sulfur-based Fertilizers on Rice Bioavailability of Cd in Soils

To explore the effects of single or combined application of chlorine-and sulfur-based fertilizers on rice bioavailability of Cd in soils, pot experiments with reddish clayey soil (developed from quaternary red clay parent materials) under three exogenous Cd levels (0, 0.5, and 2.0 mg·kg^-1) were conducted. Meanwhile, chlorine-based fertilizers (KCl, NH₄Cl) and sulfur-based fertilizersK₂SO₄, (NH₄)₂SO₄] were added in different proportions. The soil pH, Cd morphology, and Cd accumulation in rice at different growth stages were analyzed. The results revealed that both chlorine-and sulfur-based fertilizers could acidify the soil; however, the effect of chlorine-based fertilizers was more significant. During the filling stage of rice, the soil pH value of the treatment of applying single chlorine-based fertilizer decreased by 0.28 on average compared with that of applying single sulfur-based fertilizer. At the maturity stage of rice, chlorine-based fertilizer could activate the residual Cd, whereas sulfur-based fertilizer passivated the acid-extracted Cd to its residual state. Compared with the single application of the same fertilizer, the combined application of chlorine-and sulfur-based fertilizers was more likely to promote the accumulation of Cd in rice plants. The highest Cd accumulation of brown rice was 0.21 mg·kg^-1 (2.0 mg·kg^-1 exogenous Cd level) in the 1:1 (mole ratios of Cl:S) treatment of chlorine-and sulfur-based fertilizers, which was 16.4% higher than that of single chlorine-based fertilizer and 113.3% higher than that of single sulfur-based fertilizer. Therefore, the combined application of chlorine-fertilizers and sulfur-based fertilizers will increase the concentration of Cd in brown rice. To ensure food quality and safety, it is more advisable to apply single sulfur-based fertilizer for rice planting.