兰州市日光温室土壤盐分积累及离子组成变化特征

为探讨兰州市日光温室土壤盐分积累和离子组成变化特点,通过对不同耕地利用方式和种植年限条件下土壤的取样调查,分析了盐分积累特征及耕层土壤盐分离子组成变化特点,结果表明:耕地利用方式、种植年限、土壤通透性、农户经营管理水平等,都会影响日光温室土壤盐分积累和离子组成变化,普通粮田改为日光温室种植后,0~100 cm土层含盐量普遍增加,增幅达到了17.56%~29.77%,盐分表聚现象明显,耕层(0~20 cm)土壤含盐量平均增加了40%以上;随着种植年限的延长,日光温室耕层土壤盐分含量持续增加,累积量最大的离子是NO_3~-、SO_4~(2-)、Ca~(2+)和Na~+,阴离子的积累量显著高于阳离子,阴离子的组成从以HCO_3~-为主变为以NO_3~-和SO_4~(2-)为主,阳离子的组成始终以Ca~(2+)为主,同时K~+和Na~+的含量大幅度增加。盐分的大量累积,以及NO_3~-、SO_4~(2-)、Na~+等离子的相对富集,不仅会对蔬菜生长造成生理毒害、养分供需失衡、品质下降,还会引起土壤酸化、地下水污染等环境问题。

Salt accumulation and ion composition changes in soil under solar greenhouses in Lanzhou Region

Soil salt accumulation is one of the most severe soil problems in greenhouse production. Here an investigation was conducted to evaluate the dynamic changes of salt accumulation and ion composition in soils under different land uses and planting years in solar greenhouse in Lanzhou region. Results showed that salt accumulation and ion composition in the soil were affected by regional soil parent materials, hydro-geological conditions, soil permeability, farmers'' management practices, etc. When a conventional cropland was converted to solar greenhouse, soil salt content was increased by 17.56%~29.77% in 0~100 cm soil. Obvious salt accumulation occurred in topsoil(0~20 cm), with average salt content being increased by 40%. Salt content in the topsoil increased with increasing planting age. Ions NO₃^-,SO₄^2-,Ca²⁺ and Na⁺ were the most accumulated ones in topsoil, with anion accumulation being significantly higher than that of cations. Moreover, the dominating anions in the topsoil shifted from HCO₃^- to NO₃^- and SO₄^2-. However, the major composition of cations remained to be Ca²⁺, with significant increases in K⁺ and Na⁺. Salt accumulation and NO₃^-,SO₄^2- and Na⁺ enrichment not only caused physiological toxicity to vegetables, but also influenced cropping system in solar greenhouses, such as disordered nutritional supply, declined vegetable quality, soil acidification and groundwater pollution, etc.