保护地菜田与稻麦轮作田土壤微生物学特征的比较

Comparison of microbiological properties between soils of rice-wheat rotation and vegetable cultivation

比较分析了位于长江三角洲嘉兴市的三类主要水稻土(漏水型水稻土、爽水型水稻土和囊水型水稻土)由稻—麦(或油菜)轮作改为多年连作露地蔬菜和大棚蔬菜后一些土壤微生物学特征的变化,以衡量土壤质量演变的趋势。结果表明,与稻—麦(油)轮作土壤相比,蔬菜地土壤微生物区系发生了极大的变化,细菌数量显著减少,真菌和放线菌数量却显著增加;硝化细菌和反硝化细菌数量随土壤类型不同呈不同的变化。多年连作露地蔬菜和蔬菜大棚保护地土壤中微生物生物量碳和总磷脂(TPL)含量显著低于稻麦轮作土壤,土壤中脱氢酶活性也显著低于稻麦轮作土壤。Biolog分析表明,蔬菜大棚保护地土壤中微生物能利用的碳源显著少于露地蔬菜和稻麦轮作土壤,而后两者间无显著差异。说明由稻—麦(油)轮作改为多年连作大棚蔬菜后土壤微生物群落结构、功能的多样性明显下降,土壤质量的稳定性和可持续利用性———土壤的长期生产力也将大大降低。土壤微生物数量、活性及群落结构和功能多样性的下降主要与蔬菜栽培特别是大棚蔬菜栽培的旱作与稻麦水旱轮作的生态环境条件的变化和前者的过量施用精有机肥和高效NPK复合肥导致的土壤氮、磷富集、有机质下降、次生盐渍化和酸化有关。

A recent survey had been done in Jiaxing city of Zhejiang Province at Yangtze River Delta region to compare the difference of soil microbial properties among paddy soils with different cropping systems including continuous open-field vegetable cultivation, plastic-greenhouse vegetable cultivation and traditional rice-wheat rotation. The soil types included percolating paddy soil, permeable paddy soil, and waterlogged paddy soil. The results indicated that: 1) For all the three soil types, the microbial flora were markedly changed in continuous vegetable cultivation soils, especially in plastic-greenhouse vegetable cultivation soils, compared with rice-wheat rotation soils. The bacteria amounts in vegetable cultivation soils decreased dramatically, but the fungi and actinomyces amounts increased evidently. 2) Compared with rice-wheat rotation, the dehydrogenase activities in vegetable cultivation soils decreased significantly, especially in plastic greenhouse vegetable soils. 3) The microbial biomass C and total phospholipids contents (TPL) in vegetable cultivation soils greatly decreased compared with rice-wheat rotation soils. 4) Biolog analysis indicated that the kinds of carbon sources that could be metabolized by native microbes in plastic-greenhouse vegetable cultivation soils greatly decreased compared with open-field vegetable cultivation soils and rice-wheat rotation soils, revealing that microbial diversity had decreased. 5) The degradation of microbiological properties in continuous vegetable cultivation soils, especially in plastic-greenhouse vegetable cultivation soils might indicate the great decline of long-term productivity of soil and stability and sustainability of soil quality. 6) The main reasons might be associated with the environmental changes in vegetable cultivation and overuse of nitrogen and phosphorus chemical fertilizers, which caused soil acidification and secondary salinization.