不同有机废弃物对土壤磷吸附能力及有效性的影响

城郊农地是循环有机废弃物的重要场所,但长期施用畜禽粪和城市污泥可引起土壤磷素积累、磷饱和度提高,增加土壤向环境流失磷的风险。为了解施用不同来源的有机废弃物对城郊耕地土壤磷素化学行为的影响,选择4种不同磷含量的土壤,探讨在等量磷素情况下,施用KH2PO4、猪粪/稻草秸秆堆肥、沼渣、猪粪、鸡粪、生活垃圾堆肥和2种污泥等不同磷源时,土壤有效磷含量及磷吸附能力的差异。结果表明,施用有机废弃物增加了土壤有效磷和水溶性磷含量,降低了土壤对磷的吸附能力,但影响程度因有机废弃物来源而异。施用猪粪/稻草秸秆堆肥和猪粪降低土壤磷最大吸附量比例(9.03%~15.60%)与施KH2PO4(10.59%~16.63%)相当,但施用沼渣、鸡粪和生活垃圾堆肥降低土壤磷最大吸附量的比例(5.09%~9.84%)明显低于施KH2PO4;施用2种污泥降低土壤磷最大吸附量的比例(4.32%~6.77%)最小。不同有机废弃物对土壤有效磷的影响差异较小,但对水溶性磷的影响较大。施用有机废弃物后,土壤磷最大吸附量的下降值与施用有机废弃物中铁、铝、钙含量呈负相关;土壤水溶性磷的变化量与施用有机废弃物后土壤交换性钙的增加量呈负相关,表明有机废弃物中铁、铝和钙等矿质成分的增加,可在一定程度上减少有机废弃物在土壤循环处理时磷对环境的负影响。在农田施用有机废弃物时,不仅要考虑有机废弃物磷素状况,也应适当考虑其他矿质成分的组成特点。该研究可为城郊农地科学施用有机废弃物提供依据。

Effects of different organic wastes on phosphorus sorption capacity and availability in soils

Abstract: Farm in suburban area that supports dense livestock operations is important land to recycle organic wastes. Soils in this area received animal wastes and sewage sludge are vulnerable to release a large amount of dissolved phosphorus in surface runoff owing to the gradual saturation of the soil's phosphorus sorption capacity. The objective of this study was to evaluate phosphorus sorption (based on Langmuir isotherms) and availability of phosphorus (as water soluble and available phosphorus) in 4 soils incubated for 6 months with pig manure-rice straw compost, biogas residue, pig manure, chicken manure, domestic waste compost, 2 sources of sewage sludge, or KH2PO4, added to soils on a phosphorus-equivalent basis (100 mg P/kg). Phosphorus isothermal adsorption experiment was applied to evaluate the maximum adsorption capacity of the incubated soils, and both water soluble phosphorus and available phosphorus were used to assess phosphorus release potential of the soils. Results showed that all the phosphorus sources had a negative effect on phosphorus sorption and a positive effect on phosphorus availability in all soils. However, the effects on phosphorus sorption and availability in the soils varied with the phosphorus sources because of differences in their mineral components. The decreases in maximum phosphorus sorption in the pig manure-straw compost, and pig manure-treated soils (9.03%-15.60%) were similar with those in KH2PO4 treated soils (10.59%-16.63%). The decreases in biogas residue, chicken manure, and domestic waste compost treated soils (5.09%-9.84%) were much lower (P<0.05) than the KH2PO4 treated soil. The decreases in sewage sludge-treated soils (4.32%-6.77) were consistently the lowest for all incubated soils. The effects of pig manure-straw compost, biogas residue, pig manure, and KH2PO4 on water soluble phosphorus were, in most cases, greater (P<0.05) than those of other phosphorus sources. However, the effects of phosphorus sources on soil available phosphorus were relatively small. The declined values of maximum soil phosphorus sorption induced by applications of organic wastes were negatively correlated with total iron, aluminum and calcium contents in the applied organic wastes. The increased values of soil water soluble phosphorus induced by applications of organic wastes were negatively correlated to the input of calcium from these relatively high calcium sources. It suggested that increasing concentrations of iron, aluminum, and calcium in the applied organic wastes can alleviate negative impact of phosphorus on the environment when organic wastes are recycled in soil. The results provide a guideline for reasonable rate of organic waste application in the suburban areas.