The salt content,ionic composition and pH of soil in different-age vegetable fields under structure were determined in Shanghai suburbs. And the correlations between the NO3- and total salt contents of soil and the ionic concentrations of different salts were analyzed. The results indicated that (1) the salt content and electric conductivity (EC) of soil in plastic tunnels after 2 years or more were significantly higher than those in one-year-old plastic tunnels, and except HCO3- ,7 major ionic concentrations increased significantly; (2) Vegetable fields under structure took on a clear trend of soil a-cidification,and their soil pH declined to 6.38 after 6 years or more; (3) With time,ratios of NO3-, Cl- ,K+ and Mg2+ to total salt increased but ratios of SO42- and HCO3- to total salt decreased,while Ca2+ and Na+ changed little; (4) There were significant positive correlations between nitrate nitrogen content,total salt,EC and contents of major ions except HCO3-.%测定了沪郊不同年限设施菜地土壤盐分含量、离子组成和土壤pH,同时分析了土壤NO3-含量、总盐量与各类盐分离子的相关关系.结果表明:(1)设施2年及以上大棚土壤的盐分含量、电导率均显著高于1年大棚,除HCO3 -离子外,其他7种离子含量均显著提高；(2)设施菜地有酸化趋势,建成保护地蔬菜6年及以上,土壤pH降至6.38,达到弱酸水平；(3)随设施年限的增加,设施菜地NO3-、Cl-、K+、Mg2+等离子在全盐中的相对比例上升,SO42-、HCO3-则相对下降,Ca2、Na+变化不明显；(4)相关性分析表明,除HCO3外,硝态氮含量、全盐量、电导率与各离子含量均呈显著正相关.
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