水分管理、铁硅材料与生物炭对不同水稻品种吸收镉的影响及其机制

通过田间微区试验研究了三种水分管理模式干旱(D)、间歇淹水(IF)、持续淹水(CF)以及水分管理与钝化剂(铁硅材料及生物炭)联合修复模式对不同水稻品种吸收Cd的影响,并探讨其影响的可能机制。结果表明,从分蘖前期到成熟期CF处理各水稻品种糙米Cd的含量比IF处理降低0.20%～45.43%,比D处理降低37.67%～62.11%。三种水分条件下低累积水稻品种G8优2168糙米中Cd的含量比常规品种G8优165低35.03%～54.61%。施加铁硅钝化剂在三种水分(D、IF、CF)条件下,糙米中Cd含量比对应单一水分管理模式依次分别下降64.26%、55.74%、38.14%;施加铁硅+生物炭钝化剂降Cd效应下降。低累积品种+持续淹水联合铁硅钝化剂处理,糙米Cd含量最低。水稻根表铁膜中Cd含量在三种水分条件(D、IF、CF)下依次增加,根系和糙米中Cd含量则依次减少,表明持续淹水可以促进根表铁膜对Cd的固定,同时持续淹水使土壤CaCl2提取有效态Cd的含量显著下降,两者共同作用降低了糙米Cd的含量。施加铁硅钝化剂对根系铁膜固定Cd无显著影响,主要通过显著降低土壤有效态Cd使糙米中Cd含量下降。低累积水稻品种+持续淹水水分管理+铁硅钝化剂联合修复技术可以最大限度保障糙米安全生产。种植低累积水稻和在水稻生长关键期持续淹水水分管理对抑制水稻Cd吸收具有重要意义。在水稻缺水季节及缺水地区则更应重视低累积水稻品种和钝化剂的应用。

Effects of water management and amendments with iron and silicon-rich material and biochar on cadmium uptake of different rice varieties and their preliminary mechanisms

Safe food production on large areas of paddy soils that were polluted with Cd at low to medium levels is crucial for human health. The effects of three water management modes, drought(D), intermittent flooding(IF), and continuous flooding(CF)as well as the combined application of water management and amendments with iron and silicon-rich material(IS)and biochar(B)on Cd uptake by different rice varieties were investigated through a field experiment. The possible phytoexclusion mechanisms involved were discussed. The results showed that the Cd content in brown rice treated by CF from tillering to maturity stage was reduced by 0.2%~45.43% compared with IF treatment and by 37.67%~62.11% compared with D treatment. Under the three water management modes, the Cd content in the low cumulative brown rice cultivar G8 2168 was 35.03%~54.61% lower than that in the conventional variety. Under the conditions of the three modes of water management(D, IF, and CF), the contents of Cd in brown rice treated with IS amendment decreased by 64.26%, 55.74% and 38.14%, respectively, compared with that treated with only water management. The effect of the combined amendment IS+B was significantly weaker. The lowest Cd content in brown rice was obtained with the combined application of low cumulative rice varieties, continuous flooding, and IS. Furthermore, the content of Cd in rice root iron plaque varied depending on the water management mode in the following order D < IF < CF, while the content of Cd in root and brown rice showed the inverse pattern(D > IF > CF). This indicated that continuous flooding could promote the fixation of Cd by root iron plaque which acted as a barrier for Cd entering the rice plants. However, continuous flooding also decreased significantly the soil available Cd concentrations(extracted by 0.01 mol·L^-1 CaCl₂). Thus, both mechanisms contributed to reducing the Cd uptake by rice. Iron and silicon-rich material addition had no significant effect on the content of Cd fixed by root iron plaque. It reduced the rice Cd uptake mainly by significantly decreasing the Cd availability in the soil. Therefore, the combined application of a low Cd cumulative rice variety, continuous flooding and IS can guarantee safe rice production on paddy soils with low to medium Cd pollution. Planting low Cd-cumulative rice cultivars, coupled with continuous flooding during the critical growth stage are very important to limiting Cd uptake by rice. The application of amendments and low Cd cumulative rice varieties should be favored in seasons or areas with a water shortage.