不同离子微咸水对土壤水力特性和生菜生长的影响

为探究不同微咸水水质对土壤水力特性和作物生长的影响,在日光温室条件下,以生菜为供试作物开展2季盆栽试验.以CaSO₄的饱和溶液为对照(CK),向去离子水中添加不同氯化盐形成电导率相同而阳离子组成不同的微咸水处理(分别为Na⁺∶T_Na;Na⁺/K⁺比为1∶1:T_Na-K;K⁺∶T_K),研究连续灌溉下土壤容重、持水性能、水盐运移,以及生菜生长响应,并采用van Genuchten模型对水分特征曲线相关参数进行拟合分析.结果表明:与CK相比,微咸水灌溉均增加了土壤容重,降低了土壤孔隙度;随着微咸水持续灌溉,土壤孔隙分布明显改变,微小孔隙比例增加,土壤持水能力显著提高,以处理T_Na最为显著.连续微咸水灌溉下,灌溉水钠吸附比、土壤结构稳定性阳离子比与土壤进气值参数存在负相关关系(R²均为0.78).土壤中盐分逐渐积累,表现为第2季生菜生长季末(播后80 d)各处理0~20 cm土壤饱和提取液电导率较第1季显著升高,其中CK显著低于其他处理(P<0.05),且表层土壤(0~10 cm)中盐分积累更为明显.生长季末土壤表层含水量较高,与盐分分布基本一致.与CK相比,处理T_Na,T_Na-K和T_K显著降低了生菜生物量的积累(P<0.05),其中T_Na最低.

Effects of saline water with different cations on soil hydraulic properties and lettuce growth

In order to explore the effects of different saline water quality on soil hydraulic properties and crop growth, a two-season pot experiment was carried out for cropping lettuce in the solar greenhouse. Taking the saturated solution of CaSO₄ as the control(CK), different chlorides were added to deionized water to form three saline water treatments with different cationic compositions(Na⁺∶ T_Na; Na⁺/K⁺ of 1∶1: T_Na-K; K⁺∶T_K)but the same electrical conductivity. The soil bulk density, water holding properties, water and salt transport, and lettuce growth were studied. The van Genuchten model was used to fit and analyze the soil water characteristic curve and the relevant parameters. The results showed that compared with CK, saline water irrigation increased soil bulk density and reduced soil porosity. With the continuous irrigation of saline water, soil pore size distribution was significantly altered, and more micropores were formed, resulting in the improved water-holding capacity of soils. The most significant effect was observed in T_Na. Both the sodium absorption ratio(SAR)and cation ratio of soil structural stability(CROSS)showed negative correlations with the soil entry value parameters(α)(both R²=0.78). Compared with SAR, CROSS could better reflect the potential changes in soil physical properties caused by the changes in ionic compositions of irrigation water. After continuous irrigation with saline water, soil salt accumulated gradually, which was indicated by the electrical conductivity of saturated extract(EC_e)of soil at 0-20 cm depth at the end of the second season(80 days after sowing)was significantly higher than that in the first season. The EC_e of CK was significantly lower than those of other treatments(P<0.05). Salt accumulation was more evident in the surface soil layer(0-10 cm). The soil moisture content in surface layer was higher at the end of the growing season, which is basically consistent with the salt distribution. Compared with CK, T_Na, T_Na-K and T_K treatments significantly reduced lettuce growth(P<0.05), where the T_Na gave the lowest biomass.