干湿交替变化对土壤中磷形态影响及环境意义

Influence of Alternative Drying-Wetting on Phosphorus Fractions in Soils with Different Organic Matter Content and Environmental Implications

摘要: 在全球变化的背景下，干湿交替对于土壤肥力水平和水体环境质量，具有重要的研究意义。本研究采用修正Hedley土壤磷素分级方法，研究了干湿交替对不同有机质含量土壤磷形态的影响。研究结果表明，干湿交替对土壤总磷的影响不大，变异系数C.V% < 10%。干湿交替极大的改变了土壤中磷形态的分布：显著提高了土壤有效磷(尤其是树脂磷)和有机磷(NaHCO3-Po，NaOH-Po和Con.HCl-Po)的含量，同时降低了土壤中NaOH-Pi和闭蓄态磷的含量。在干湿交替条件下，有机土中树脂磷提高了121%，而贫瘠土中树脂磷仅提高了31%，这说明干湿交替对有机质含量高的土壤活性磷影响更为显著。该研究表明干湿交替促进了土壤中磷由闭蓄态磷向活性磷和有机磷的转化。在全球变化的背景下，干湿交替可以提高土壤中有效磷含量，促进作物的生长；但当有降水或灌溉时，也可能加剧土壤中磷素的流失，从而引发近海富营养化事件，对于近海环境质量和区域生态安全可能构成威胁。

Abstract: In the context of global change, it is of significance to study the effect of alternative drying-wetting on the soil fertility level and the environmental quality of water body. In this study, soil P was fractionated by using a modified Hedley fractionation method to examine the effect of alternative drying-wetting on phosphorus fractions in soils with different organic matter content. The results displayed no significant difference of total phosphorus between the two treatments because the coefficient of variance was less than 10%. However, there is a significant change in the distribution of soil phosphorus fractions: increase the content of labile-P (especially resin-P) and organic-P (NaHCO3-Po, NaOH-Po and Con.Hcl-Po) while decreasing the content of NaOH-pi and occlude-P. Under the alternative drying and wetting condition, resin-P increased by 121% in the organic soil, while only increasing by 31% in the sterile soil, which indicates a significant effect of alternative of drying and wetting on labile-P in soils with high organic matter content. The study indicates that alternative drying and wetting seemed to drive the phosphorus transformation from the occlude-P to labile-P and organic-P. In the context of global change, alternative drying and wetting can increase the content of labile P in the soil to improve crop growth. However, when there is rainfall or irrigation, it may aggravate the loss of soil phosphorus, which will induce the offshore eutrophication and possibly threaten the coastal environmental quality and regional ecological security.