秸秆还田配施无机改良剂对稻田土壤镉赋存形态及生物有效性的影响

以成都平原德阳市旌阳区Cd污染稻田土为研究对象,通过大田试验研究了秸秆还田下配施无机改良剂对污染稻田土壤Cd形态分布特征及水稻生物有效性的影响。结果表明,秸秆(油菜秆、小麦秆)配合改良剂(海泡石、石灰、钙镁磷肥)施用均显著降低水稻糙米Cd含量,其中油菜秸秆配合海泡石效果较优,降低幅度为36.75%;油菜秸秆配合改良剂(海泡石、石灰、钙镁磷肥)施用提升了茎秆Cd含量(31.46%~140.73%),可能会影响秸秆还田利用。对土壤可交换态Cd含量影响表现为:水稻分蘖期,小麦秸秆配合石灰处理降低50.47%,效果较佳;水稻成熟期,小麦秸秆配合钙镁磷肥处理降低58%,效果较优。回归分析结果表明,土壤Cd形态由有效性较高的形态(可交换态)向有效性较低的形态(铁锰氧化物结合态、有机结合态等)转化,有助于减少水稻根系对Cd的吸收,降低糙米Cd的累积。综上,在抑制土壤活性态Cd,降低水稻Cd积累方面,油菜秸秆还田配合海泡石和小麦秸秆还田配合石灰效果均较优。

Effects of combined application of straw and inorganic amendments on cadmium speciation and bioavailability in paddy soil

To investigate effects of straw and inorganic amendments on cadmium(Cd) speciation and bioavailability in paddy soil, field experiments were conducted in Jingyang County, Deyang. The results showed that Cd content decreased significantly by combined application of straw-returning(rape straw and wheat straw) and inorganic amendments(sepiolite, lime and calcium magnesium phosphate fertilizer) in brown rice. Cd content in brown rice was decreased by 36.75% under rape straw and sepiolite, co-treatment. However, Cd content in the stem increased by 31.46%~140.73% after the combination application of rape straw with three inorganic amendments. The increasing might have a negative effect on straw returning and utilization. At the tillering stage of rice, the combination use of wheat straw and lime exhibited more efficient in decreasing exchangeable Cd in soil, which was decreased by 50.47%. At the mature stage of rice, the combination use of wheat straw with calcium magnesium phosphate fertilizer exhibited more efficiency in decreasing exchangeable Cd in soils, which was decreased by 58%. According to the regression analysis, soil Cd speciation transformed from higher availability to lower availability, thus reducing Cd accumulation in rice. Therefore, the combination application of rape straw with sepiolite, and wheat straw with lime application showed more efficiency in decrease of soil Cd availability, as well as the Cd accumulation in rice.