集约化露天菜地表层土壤盐分累积特征及消长规律

Accumulation characteristics and seasonal variation of surface soil salts in open vegetable fields under intensive vegetable production

以广东省佛山市南海区为例，研究了集约化露天菜地表层土壤盐分的累积状况和离子组成，对盐分的季节性消长规律及其变化原因进行了深入分析。结果表明：2006年春季土壤盐分的累积情况较为严重，5个集约化露天菜地样点中有3个样点（1、2、4号）的表层土壤盐分浓度较高，全盐质量分数超过1．0g·kg^-1，已达到次生盐渍化的标准，其中又以2号样点（菜场）最为突出，全盐质量分数高至2．42g·kg^-1；2006年容季到夏季为脱盐阶段，土壤盐分浓度下降明显；2006年夏季到秋冬季变化幅度不大。土壤盐分浓度的变化与降雨量有密切关系，虽然2006年降雨偏多，但佛山市南海区农业集约化水平较高，部分菜地连年种植蔬菜、复种指数极高、化肥施用量偏大，从而在遇到干旱年份和季节，集约化露天菜地土壤仍有发生次生盐渍化的风险。土壤盐分的离子组成上，阳离子以Ca^2＋为主，占全盐质量分数的11．0％～24．1％；阴离子以NO3^-和SO4^2-为主，分别占全盐质量分数的8．9％～31．0％和10．9％～45．7％。研究结果可为控制土壤盐分累积、提高蔬菜生产能力及品质、保护和合理利用耕地资源，提供参考资料。

In this paper, Nanhai district of Foshan city, a typical area of Pearl River Delta region, was chosen for the risk assessment of soil secondary salinization. Due to long-term vegetable cropping, high level of multiple cropping index, and high application rate of nitrogen fertilizer, the salt accumulation status and salt ion composition of surface soils in five open vegetable fields under intensive vegetable production in Nanhai were investigated, and the seasonal variation of surface soil salt contents was analyzed and its reasons were further discussed. The results indicated that the surface salt contents in the spring of 2006 were the highest among the three samplings, the surface soil salt contents declined from spring to summer of 2006, and the change of surface soil salt contents was not obvious from summer to autumn/winter of 2006. The variation of surface soil salt contents was related to rainfall greatly. It was also found that the main cation in surface soils was Ca^2＋, and the main anions were NO3^- and SO4^2- according to the composition of surface soil salt ions. The outcome of this study could offer references for controlling surface soil salt accumulation, improving the yield and quality of vegetables, protecting the arable land and using it reasonably.