紫色土水分特征曲线室内测定方法的对比

为探寻全吸力范围内土壤水分特征曲线的可靠测定方法,采用沙箱排水法、Hyprop仪蒸发法、压力膜仪排水法和露点水势仪蒸发法分吸力段测定盐亭紫色土耕地表层2~7 cm和亚表层7~12 cm土壤的水分特征曲线,对比测定结果的方法间差异,并分析其原因。结果表明:对于表层和亚表层土壤,低吸力段(h >-100 cm)水分特征曲线的沙箱法和Hyprop仪法的均方根误差E_RMS (θ)均较小,在0.026~0.082 cm3/cm3范围内,确定系数R2均大于0.962,说明这两种方法测定结果之间差异不大。高吸力段(h <-330 cm)的压力膜仪法与露点仪法测定结果之间的差异较大,E_RMS (θ)为0.062~0.097 cm3/cm3,R2较低,为0.775~0.952。因此,全吸力范围内水分特征曲线测定方法的选择与组合应考虑土壤孔径分布特征和研究目的。

Comparison of laboratory methods for determining water retention curves in purple soil

Four laboratory methods, namely, the sand box, the HYPROP system, pressure plates and the dewpoint potential meter, were used to determine soil water retention curves (SWRC) for samples of farmland purple soil. SWRC were determined over the whole entire moisture range for samples obtained from two horizons (i. e., 2-7 cm, 7-12cm). Measured data was compared to identify the most reliable method. The root-mean-square errors of the soil water content (E_RMS(θ)), established under low suctions (h>-100 cm), the sand box and HYPROP system were small (0.026-0.082 cm³/cm³) with the coefficient of determination (R²) between measured water retention curves by the two methods being greater than 0.962. Contrastingly, the E_RMS(θ) of soil water content, established under high suctions (h<-330 cm), using pressure plates and the dewpoint potential meter were larger (0.062-0.097 cm³/cm³), with lower R² values (0.775-0.952). In conclusion, the selection and combined use of appropriate methods for SWRC determination, over the entire soil moisture range, should be decided upon according to the soil's pore size distribution and the application objective.