稻麦轮作田改为菜地后生化指标的变化

本文初步分析比较了位于长江三角洲嘉兴市的3种主要土壤类型漏水型水稻土、爽水型水稻土和囊水型水稻土由稻-麦(油菜)轮作田改为多年连作保护地菜田后一些生物化学指标的变化。结果表明:由稻麦轮作田改为蔬菜露地和大棚蔬菜保护地后都可引起土壤的酸化,pH下降程度随土壤类型不同而有别,其中漏水型水稻土和爽水型水稻土由稻麦轮作田改为大棚蔬菜保护地后pH下降最为强烈,分别下降1.96和1.87个单位。与稻-麦(油菜)轮作土壤相比,蔬菜露地和大棚蔬菜保护地土壤脱氢酶活性都显著降低,其中后者降低程度远大于前者;土壤转化酶和中性磷酸酶活性都有不同程度的降低。这些结果说明由稻麦轮作田改为多年连作蔬菜露地和大棚蔬菜保护地后引起土壤微生物活性的下降,从而影响土壤生物化学过程,进而影响土壤的健康质量。

CHANGES IN SOIL BIOCHEMICAL PROPERTIES CAUSED BY CROPPING SYSTEM ALTERATION FROM RICE-WHEAT ROTATION TO VEGETABLE CULTIVATION

A survey has recently been done in Jiaxing City of Zhejiang Province at the Yangtze River Delta to determine changes in soil biochemical properties in paddy soils with the traditional cropping system of rice-wheat rotation altered into vegetable cultivation, including continuous plastic mulching vegetable cultivation, and plastic greenhouse vegetable cultivation. Results show alteration of the cropping system induced soil acidification and soil pH dropped to an extent varying with type of the soil (Percolating paddy soil, Permeable paddy soil, and Waterlogged paddy soil). The activities of several soil enzymes including dehydrogenase, urase, inverase and phosphase in soils under plastic mulching vegetable cultivation (MVC) were all lower than under rice-wheat rotation (RWR), and under plastic greenhouse vegetable cultivation than under MVC and RWR. The decreases in biochemical properties in the soils under continuous vegetable cultivation, especially under plastic greenhouse vegetable cultivation, might be caused by soil acidification and overuse of nitrogen and phosphorus fertilizers.