长期施肥条件下菜田—蔬菜生态系统变化的研究(Ⅱ)土壤理化性质的变化

 随着土壤有机质含量的提高，大约占土壤全氮含量95% 的可矿化氮量也随之增加，土壤供氮能力增强；而单施氮素化肥以及在此基础上配施磷钾肥的处理，土壤中氮库难以扩大，碱解氮的含量急剧下降。在设施内长期施肥后土壤全磷富集，钾素不足。长期偏施过量无机氮肥加速了土壤的酸化及交换性盐基数量的下降及其比例的失调，设施栽培长期施用有机肥以及氮磷钾配施可阻止其进程。土壤物理性退变是从量变到质变的长期过程，对土壤的破坏性很大。

Studies on Changes of Field-Vegetable Ecosystem under Long-term Fixed Fertilizer Experiment

With the increase of soil organic matter, the mineralizable nitrogen, which is about 95 percent of soil total nitrogen, was also increased, thus soil can provide more nitrogen. In the treatments with application of nitrogen alone or combination with phosphorous and potassium, it was difficult for the N sink to be enlarged, so the available nitrogen was decreased quickly. Long-term fertilization trial in protected field showed that the soil was rich in total phosphorus and lack of potassium. Excessive and long-term application of inorganic nitrogen alone accelerated the progress of soil acidization, decreased the exchangeable bases and their proportion was in disorder. Such problems can be prevented by application of organic matter, protected cultivation and combination with phosphorus and potassium. Soil physical degradation was a long-term progress from quantity change to quality change and it was destructive to soil productivity.