改良剂配合水分管理减少水稻吸收土壤中镉的研究

为研究减少水稻籽粒中镉的积累,选择一中度重金属污染农田,进行了4种改良剂处理(不施改良剂、生物质炭、钙镁磷肥—坡缕石—硫磺粉(比例为100∶50∶1)和石灰—沸石—硫磺粉(比例为100∶50∶1))和2种水分管理模式(深灌和浅灌)的不同组合处理,田间试验研究了改良剂配合水分管理减少水稻吸收土壤镉的效果,改良剂用量为3 t/hm~2。结果表明,施用改良剂和采取深灌均可显著减少水稻从土壤中吸收镉,并以二者配合的效果最佳。与浅灌/不施改良剂处理比较,钙镁磷肥—坡缕石—硫磺粉和石灰—沸石—硫磺粉2种复合改良剂配合深灌可分别降低籽粒中镉含量56.53%和55.53%,但施用生物质炭降低水稻吸收土壤中镉的效果相对较差。施用复合改良剂促使土壤中交换态镉转化为碳酸盐结合态、氧化物结合态及残余态镉等较为稳定的镉形态,降低了土壤中生物有效态和水溶态镉,减少了水稻吸收土壤镉;深灌有利于硫化镉的形成,并通过稀释作用降低水稻吸收土壤镉。研究认为改良剂配合深灌是一种较为方便、有效的技术,适用于农田土壤镉污染的控制。

Reduction of Cadmium Uptake of Rice Plant from Soil by Application of Amendments Combined with Water Management

Reducing the accumulation of cadmium in the rice grain is the important target of heavy metal pollution control in China. In this study, a field experiment was conducted in a moderate heavy metal contaminated farmland to study the combined effects of applying amendments and water management on reduction of cadmium uptake of rice plant from soil. The field experiment included eight treatments, i.e., no amendment + shallow irrigation (control), biochar + shallow irrigation, calcium magnesium phosphate-palygorskite-sulfur powder (100:50:1) + shallow irrigation, limestone-zeolite-sulfur powder (100:50:1) + shallow irrigation, no amendment + deep irrigation, biochar + deep irrigation, calcium magnesium phosphate-palygorskite-sulfur powder + deep irrigation, and limestone-zeolite-sulfur powder + deep irrigation. Total dosage of all various amendments was 3 t/hm². The results showed that the uptake of cadmium by rice plant from soil was reduced significantly by the application of amendments and deep irrigation. Combined effects of both amendments and deep irrigation were greater than those of amendments or deep irrigation. Compared with the control, the contents of cadmium in the grain for treatments of calcium magnesium phosphate-palygorskite-sulfur powder + deep irrigation and limestone-zeolite-sulfur powder + deep irrigation were reduced by 56.53% and 55.53%, respectively. Effect of biochar on reducing the uptake of cadmium was relatively small. The application of the compound amendments could convert the exchangeable cadmium in the soil into relative stable form of cadmium such as carbonate bound, oxide bound and residual forms, and thus reduce the bioavailability of cadmium in soil and the uptake of cadmium from soil. Deep irrigation could enhance the soil reduction and the formation of cadmium sulfide, and achieved the purpose of reducing the uptake of cadmium from soil by dilution effect. The result suggested that application of amendments combined with deep irrigation was a convenient and effective technique to control cadmium uptake of rice plant from soil.