适度深耕配施有机肥减少蔬菜对土壤重金属的吸收

Reducing Uptake of Heavy Metals by Vegetables from Contaminated Soils under Application of Appropriate Deep Tillage Combined with Organic Fertilizer

为了解常规农业措施在污染农田安全利用实施中的效果,选择轻度和中度2种重金属污染农田,分别开展了3种耕作深度(20、30和40 cm)与2个有机肥施用水平(0、30 t/hm^2)的不同组合试验,探讨了深耕对土壤剖面中重金属分布与蔬菜吸收土壤重金属的影响。结果表明,深耕(30、40 cm)可显著稀释0~20 cm土壤重金属水平,减少蔬菜吸收土壤中的重金属,降低效果随耕作深度的增加而增强。深耕后,轻度污染土壤上生长的蔬菜中重金属含量都在标准值以下;但中度污染土壤上生长的蔬菜中部分重金属仍存在超标现象;在深耕同时,增施凹凸棒石+石灰混合改良剂可降低土壤中重金属的生物有效性,显著降低蔬菜对中度污染土壤中重金属的吸收。研究也发现,深耕后0~20 cm土层土壤有机质和全氮、有效磷、有效钾含量也因稀释而下降,并导致蔬菜生物量的下降,但配施有机肥可减轻因深耕引起的副作用。研究认为,适度深耕配施有机肥适用于轻度污染土壤的修复,用于中度污染土壤修复时还需要适当增施化学改良剂。

To understand the effect of conventional agricultural measures on the safe utilization of polluted farmland, we selected two kinds of farmland soils polluted slightly and moderately by heavy metals for experiment. Different combinations of three tillage depths(20 cm, 30 cm and 40 cm) and two levels of organic fertilizer application(0 and 30 t/hm^2) were carried out. The distribution of heavy metals in soil profiles and vegetable uptake affected by deep tillage were discussed. The results showed that deep tillage(30 cm and 40 cm) could significantly dilute the concentrations of heavy metals in 0~20 cm soil, reduce the uptake of heavy metals by vegetables, and the reduction effect increased with the increase of tillage depth. After deep tillage, the concentrations of heavy metals in vegetables grown on slightly polluted soils were all below the standard values. However, some heavy metals in vegetables grown on moderately polluted soils still exceeded the standard value. Meanwhile deep tillage with the amendment application of both attapulgite and lime could reduce the bioavailability of heavy metals in soils and significantly reduce the uptake of heavy metals by vegetable from moderately polluted soils. It was also found that organic matter, total nitrogen, available phosphorus and available potassium in 0~20 cm soil layer also decreased due to dilution after deep tillage, which led to the decrease of vegetable biomass. But the side effects caused by deep tillage could be alleviated by applying organic fertilizer. It was concluded that appropriate deep tillage combined with organic fertilizer was suitable for the remediation of slightly polluted soils, and chemical amendments were also needed for the remediation of moderately polluted soils.