不同水分管理模式对水稻吸收土壤砷的影响

通过水稻盆栽试验,研究了淹水灌溉(F)、灌浆期前湿润灌溉(A-F)、灌浆期后湿润灌溉(F-A)、淹水与湿润交替(AFA)这4种水分管理模式对水稻吸收土壤As的影响.结果表明,同F处理比较,A-F处理能显著降低水稻根和茎叶As含量,F-A和AFA处理都能显著降低水稻茎叶、谷壳、糙米As含量和糙米无机As含量.A-F、F-A、AFA处理对水稻生物量影响都不大,仅AFA处理减少了水稻根系生物量.F-A和AFA处理降低糙米As含量的机理是:灌浆期是水稻糙米吸收土壤As的关键时期,此时的湿润灌溉提高了土壤E h,土壤溶液As(Ⅲ)与As(Ⅴ)浓度之和、As(Ⅲ)/As(Ⅴ)的比例都显著降低,从而使土壤As的迁移能力得到抑制.F-A处理降低水稻糙米总As和无机As含量的效果与AFA处理无显著差异,但F-A处理的操作更简单,因此,F-A处理应当是污染土壤中控制水稻糙米累积As的最佳水分管理模式.

Effects of different water management modes on soil arsenic uptake by rice plants

A pot experiment was conducted to study the effects of four modes of water managements on soil arsenic (As) uptake by rice plants. These four modes were flooding throughout the entire period of rice growth (F), aerobic flooding before flowering stage (A-F), aerobic flooding after flowering stage (F-A), and alternate flooding and aerobic during flowering stage (AFA). The results showed that, compared to F, A-F reduced As contents in rice roots and straws significantly, while F-A and AFA reduced As contents in the straws, husks and grains of rice plants, and also reduced inorganic As in grains significantly. A-F, F-A and AFA showed little effects on rices biomass, but AFA resulted in decreases in the biomass of rice roots. The mechanisms of F-A and AFA reducing As contents in rice grains were supposed. Aerobic flooding during flowering stage, a key period of soil As uptake by rice plants, enhanced soil Eh values, which resulted in significantly decrease in the sum of As³⁺ and As⁵⁺ contents and the ratio of As³⁺/As⁵⁺, hence restrained transfer of soil As to rice plants. There were no obvious differences between F-A and AFA in reducing contents of total As and inorganic As in rice grains; however, F-A was an easier mode to apply than AFA in rice planting, indicating that F-A was more promising in water managements to reduce As uptake by rice plants in As contaminated soils.