大安灌区盐碱土土壤水分扩散特征研究

Study on Saline-alkali Soil Moisture Diffusivity in Da'an Irrigation District

土壤水分扩散率是研究盐碱地土壤水盐运移的重要参数之一。运用水平土柱入渗法对大安灌区典型盐碱土剖面进行了土壤水分扩散试验,结果表明:剖面各层土样湿润锋迁移速率不同,但具有相同的变化规律;湿润锋迁移速率与时间成显著地负相关关系,经拟合分析二者呈幂函数变化;体积含水率相同时,不同厚度土样的土壤水分扩散率不同,但并没有按照由上向下逐渐递减的规律变化,其中,40～60cm土层土壤水分扩散率最快,其次为0～20cm土层、20～40cm土层、80～100cm土层,最慢的为60～80cm土层;土壤水分扩散率随体积含水率的增加呈指数函数增长变化,经相关分析达到显著水平,且拟合优度均在0.82以上;土壤容重和土壤含盐量均对土壤水分扩散率有影响。

Soil moisture diffusivity is one of the essential parameters to study water and salt motion in saline-alkali soil. The saline-alkali soil moisture diffusivity feature of Da＇an irrigation is simulated by horizontal soil column method. The results show that the wetting front migration rate of different soil profile layers is different, but the variation rule is the same; there exists significant negative correlation between wetting front migration rate and time; through fitting analysis ,it is found that and the relationship between wetting front migration rate and time is power function; the soil moisture diffusivity is different in different thickness of soil with same volumetric soil moisture content, but not according with the change rule of the gradual increase up to down. The soil moisture diffusivity changes fastest in 40-60 cm layer, then descending as 0--20 cm layer,20-40 cm layer,80-100 cm layer, and the 60-80 cm layer is the slowest. It changes with volumetric soil moisture content in every soil layer as harp positive exponential function, and these relationships are significant with statistical analysis and all of their fitting goodness are above 0. 82; soil moisture diffusivity are influenced by soil bulk density and soil salinity.