秸秆及生物炭添加对猪粪沼渣施肥水稻重金属积累的影响

秸秆还田在重金属污染稻田中被广泛应用并日益推广,其对土壤中重金属生物有效性和水稻重金属吸收积累产生的影响不容忽视.本研究选用因连续10年以上施用生猪沼渣沼液而导致重金属超标的水稻土,通过盆栽试验研究了不同的秸秆还田方式(直接还田或生物炭还田)与用量(0、1%、2%、4%和8%)对水稻重金属吸收积累的影响.结果表明,长期施用沼渣沼液可导致土壤重金属富集,其中,铜(Cu)、锌(Zn)和镉(Cd)含量高于国家土壤环境质量二级标准;秸秆或生物炭添加提高了水稻根或茎叶中重金属的截留,降低了籽粒中的积累;秸秆还田对于水稻Cu的吸收积累控制效果显著,添加1%、2%、4%和8%的秸秆分别使糙米中的Cu含量降低了35%、51%、64%和71%;生物炭添加对于控制水稻Cd的吸收积累效果显著,1%、2%、4%和8%生物炭添加量分别使水稻Cd的积累降低了21%、33%、36%和35%.对于Zn的吸收积累,两种还田方式均具有显著的控制效果;但在As污染稻田,秸秆直接还田应慎重,因为秸秆添加可显著提高糙米中As的积累.通过对比不同的秸秆还田量对控制糙米中重金属积累的效果,同时考虑该区域重金属的污染状况和还田成本,推荐在该施肥区域实施2%的秸秆直接还田.该研究将为水稻安全生产与农业废弃物循环利用提供理论与实践指导.

Effects of straw and biochar application on heavy metal accumulation in rice fertilized with pig-biogas residues

Straw incorporation is widely performed in heavy metal contaminated paddy fields, which may significantly affect the bioavailability of heavy metals in soil and consequently alter heavy metal accumulation in rice grains. In this study, we carried out a pot experiment to investigate the effects of different ways (direct incorporation or bio-char incorporation) and dosages (0, 1%, 2%, 4% and 8%) of straw incorporation on the accumulation of heavy metal in rice plants. For the pot experiment, soil was sampled from paddy fields which had been long-term fertilized with pig-biogas residue. The results showed that long-term fertilization with pig-biogas residues resulted in heavy metal accumulation in paddy field, and soil cadmium (Cd), copper (Cu) and zinc (Zn) concentrations exceeded the limits of the Chinese soil environmental quality standard. Straw or biochar incorporation increased the retention of heavy metals in rice roots or shoots, thus decreasing the accumulation of grains. Straw incorporation significantly reduced Cu uptake and accumulation in rice. Applying 1%, 2%, 4% and 8% of straw decreased Cu concentration in brown rice by 35%, 51%, 64% and 71%, respectively. Bio-char incorporation significantly reduced Cd accumulation in rice. Addition of 1%, 2%, 4% and 8% of bio-char decreased Cd accumulation in rice plant by 21%, 33%, 36%, and 35%, respectively. Both straw incorporation ways significantly reduced Zn accumulation in rice, while straw incorporation was not suitable for arsenic contaminated paddy soil as it could significantly increase As accumulation in brown rice. By comparing the efficiency of reducing heavy metal accumulation in rice plants and the cost of straw incorporation, 2% of straw incorporation was recommended for the studied fields. The results of this study will provide theoretical and practical guidance for the safe production of rice and the recycling of agricultural wastes.