水分管理与施硅对水稻根表铁膜及砷镉吸收的影响

为探明水分管理与施硅对土壤砷（As）/镉（Cd）生物有效性、水稻根表铁膜与As/Cd吸收的影响，以贵州省开阳县某砷镉复合污染水稻土为供试土壤，进行了水稻盆栽种植.设5种水分管理模式：全生育期淹水（T1）；移栽到抽穗后三周（0~105 d）淹水，其余时期湿润灌溉（含水率50%~60%）（T2）；移栽到抽穗前三周（0~65 d）淹水，抽穗到抽穗后三周（84~105 d）淹水，其余时期湿润灌溉（T3）；抽穗到抽穗后三周（84~105 d）淹水，其余时期湿润灌溉（T4）和全生育期湿润灌溉（T5）.硅设不施硅和施硅这2个水平.结果表明，淹水/湿润灌溉较单一淹水或单一湿润灌溉更利于根表铁膜（DCB-Fe）的形成，DCB-As/Cd含量随DCB-Fe含量升高而升高；施硅使土壤pH升高，有效As/Cd含量降低，DCB-As含量增加，除淹水处理外的DCB-Fe/Cd含量降低.淹水时间越短，水稻各部位对Cd积累量越高，对As积累量越低.施硅使水稻各部位生物量升高，As/Cd含量降低.其中根、茎、叶和籽粒的Cd含量分别降低4.23%~31.06%、11.41%~52.90%、1.74%~35.73%和19.25%~39.76%，As含量分别降低1.47%~52.60%、6.12%~63.02%、2.97%~28.41%和16.33%~61.23%.5种水分管理中，施硅结合T3水分管理可以实现水稻生物量最高及水稻对砷镉吸收量最小.因此，根据As/Cd实际污染情况合理进行水分管理与施硅可以有效降低土壤As/Cd生物有效性进而减少水稻对As/Cd的累积，实现农田安全生产.

Effects of Water Management and Silicon Application on Iron Plaque Formation and Uptake of Arsenic and Cadmium by Rice

To explore the effects of water management and silicon application on the bioavailability of soil arsenic (As) and cadmium (Cd), and the accumulation of As and Cd in rice, pot experiments were carried out using As/Cd co-contaminated paddy soil from a field in Kaiyang County, Guizhou Province. The experimental treatments had the following five water application modes with and without silicon addition:flooding during the entire growth period (T1); flooding for three weeks (0-105 d) after transplanting with wet irrigation (moisture content 50%-60%) during other growth periods (T2); flooding for three weeks before heading (0-65d), three weeks after heading (84-105d), and wet irrigation during other growth periods (T3); flooding from heading to three weeks after heading (84-105d) and wet irrigation during the other growth periods (T4); and wet irrigation during the entire growth period (T5). The results showed that compared with flooding and wet irrigation, flooding combined with wet irrigation was more conducive to the formation of iron plaque (DCB-Fe) on the surfaces of roots. As and Cd content increased with an increasing of content of DCB-Fe. Silicon application increased soil pH and the content of DCB-As but decreased available As and Cd in the soil and, with the exception of the flooding treatment, the DCB-Fe/Cd content. The shorter the flooding time, the higher the accumulation of Cd and the lower the accumulation of As in each part of the rice. Silicon application increased the biomass of rice but decrease the Cd content of roots, stems, leaves, and grain by 4.23%-31.06%, 11.41%-52.90%, 1.74%-35.73%, and 19.25%-39.76%, respectively. Silicon application also decreased the As content of roots, stems, leaves, and grain by 1.47%-52.60%, 6.12%-63.02%, 2.97%-28.41%, and 16.33%-61.23%, respectively. Among the five modes of water application tested, silicon application combined with the T3 mode achieved the highest rice biomass and lowest rice As and Cd contents. Therefore, it is suggested that selecting water management and silicon application regimes according to the level of As/Cd pollution can effectively decrease the bioavailability of As/Cd in the soil, thereby reducing the accumulation of As/Cd in rice.