盐分浓度和钠浓度对蒙脱土保水性的影响

为了预测使用干燥地、半干燥地的再利用水灌溉给土壤构造带来的影响，调查了盐分浓度和钠吸附比（SAR）给蒙脱土的保水性带来的影响．用电导率（EC）表示盐分浓度，使用了NaCl12，20，50mol·m^-3和SAR5，10，20组合的溶液进行试验．当NaCl2mol·m^-3时由于EC低，所以全部的SAR显示高的保水性．因为EC变高，当NaCl20mol m^-3时SAR5跟SAR10相比保水性大幅度降低．在凝集条件下，保水性与SAR同时增加，在分散条件下没发现保水性的变化．在凝集状态下EC越高或SAR越低的时候，保水性降低．可以认为蒙脱土显示低保水性的时候会变成凝集构造．要控制蒙脱土的物理性质，盐分浓度和SAR的组合是很重要．

Effect of Salinity and Sodicity on Water Retention of Montmoriilonite

Irrigation with used low quality water in arid and semiarid regions may damage soil structure to clay dispersion. We investigated water retention of montmorillonite affected by salinity and sodicity, which are indicated by electrical conductivity （EC）and sodium adsorption ratio （SAR）, respectively. Experiment was carried out with solutions of NaCl 12,20,50,mol m-3, combined with SAR 5,10,20.When NaCI concentration was 2 mol m-3, the clay showed high water retention at all SAR owing to low EC. At NaCl 20 mol m-3,the sample SAR 5 showed significantly low water retention compared to SAR 10becanse EC of the former solution was high. Water retention increased with increasing SAR when was in coagulative condition, both EC and SAR affected the water retention, and lower water content was observed at higher EC and lower SAR. For montmorillonite, this lower water retention might lead to an aggregated structure.Thus,combined effect of salinity and sodicity was found important for controlling physical properties of momtmonitic soils.