不同利用年限设施栽培土壤金属元素含量的变化

Variations in metal elements contents of greenhouse soils with different vegetable growing years

以农田和露天菜地为对照，研究了晋北地区不同利用年限设施栽培土壤金属元素含量的变化。结果表明，由农田改为设施栽培菜地后，随着利用年限的增加，不同土层中K、Ca、Mg、Al、Cd和Li含量表现出“降低—升高—降低”的变化规律，Fe、Mn、Cu和Cr含量则呈现“升高—降低—升高”的变化规律。进一步方差分析表明，不同处理之间，同一土层金属元素含量差异达显著水平（P＜0.05）。表层土壤中K、Na、Al、Fe、Mn和Cu含量值均比第二次全国土壤普查时含量值高，而露天菜地和设施栽培土壤Ca、Mg含量差异不明显。依据中国土壤环境质量评价标准，当地设施栽培土壤Cd、Cu和Cr含量均没有超标，但土壤Cd含量偏高，整体分布在0.28～0.56 mg·kg^-1的范围内，接近我国土壤环境质量Ⅱ级标准上限1 mg·kg^-1。

With cropland filed and open vegetable fields as control, the experiment was carried out to study the change of contents of K, Na, Ca, Mg, Al, Fe, Mn, Cu, Cd, Cr, and Li in different layers （0～20, 20～40 cm） of greenhouse soils with six vegetable growing years （1, 4, 7, 11, 14 a, and 17 a） in northern Shanxi. The results indicated that K, Ca, Mg, Al, Cd and Li contents in greenhouse soils decreased during the first 4 years, then increased until 14th year, and decreased after that. Fe, Mn, Cu and Cr contents increased during the first four years, then decreased to the 11th year, and increased after that. The analysis of variance showed significant difference in minerals content of the same soil layer between different treatments. Contents of K, Na, Al, Fe, Mn, and Cu were higher than the natural background soil metal concentrations of northern Shanxi, whereas Ca and Mg showed no significant change. According to environmental quality standard for soil pollution, the contention of Cd, Cu, and Cr fell into the allowable range, while that of Cd was above the upper limit. In addition, Cd was within the range of 0.28～0.56 mg·kg^-1, nearly approaching to the maximum threshold.