长期定位施用氮肥对菜田土壤肥力变化的影响

在蔬菜氮肥长期定位试验条件下研究了不同施肥处理对土壤肥力变化的影响。明确了长期施用有机肥对增加菜田土壤有机质含量的作用及其变化过程，施用氮素化肥对增加土壤有机质含量作用不大以及土壤有机质分解的缓慢过程。虽然施用有机肥对维持土壤养分平衡有着积极作用，但长期不施磷、钾肥仍然会导致土壤磷、钾养分的亏缺。在偏施特别是多施氮素化肥条件下，土壤交换性盐基总量及交换性Ｃａ２＋、Ｍｇ２＋含量明显下降，土壤ｐＨ值降低，逐渐向酸性方向恶化。从施肥角度提出了防止菜田土壤恶化的对策。

Effect of Long-term,Fixed Position Nitrogen Application on Variation of Soil Fertility in Vegetable Field

Under the condition of long-term and fixed position nitrogen application in vegetable field,the effect of nitrogen application treatments on variation of soil fertility was investigated. Results showed that long-term organic manure application could increase the content of organic matter in the soil,its variation process was observed. Inorganic fertilizer had no effect on organic matter increase,the slow process of soil organic matter degeneration was also proved. Although organic fetilizer could improve the balance of soil nutrition,phosphorus and potassium would still be deficient without their supplement. Partiality for nitrogen application,especially its over application would result in decreases of total exchangable base,and exchangable Ca 2 and Mg 2 in the soil,which could speed up soil acidation. The strategy for preventing siol deterioration is discussed in point of fertilizer application.