土壤水盐运动模式研究及其在干旱区农田的应用

Model on Water-Salt Movement and Application in Field of Arid Land

采用预估校正法求解土壤水分运动的h型Richards方程 ,此方法可以控制一定的迭代步数 ,但同样可达到二阶精度。同时采用具有二阶高精度的差分法求解土壤盐分运移的对流扩散方程 ,此格式可避免采用一般差分格式时出现的数值弥散问题。并将上述数学模式对干旱区绿洲棉田 ,在蒸散条件下土壤水分运动和土壤盐分向上运动积累过程进行数值模拟 ,模拟结果与测量值吻合较好 。

The Prediction-Correction method is applied to solve the \%h\% type of Richards equation for water movement in soil. Satisfactory precision is gotten while the iteration steps are constrained by this method. Furthermore, the quadratic upstream interpolation difference method is adopted to solve the convection-diffusion equation for soil salt movement. It can avoid the problem of numerical dispersion and presents steeper apex of soil salt profile. Finally, this mathematical model is also utilized to simulate water-salt movement and the process of upwards accumulation of soil salt in cotton field of arid land under the condition of evaporation. The numerical results turn out in good agreement with the experimental data, thus the mathematical model may provide seientific basis for predicting salinization of soil. The water-salt movement in cropland with canopy and evaporation influence may be calculated by the present model, and the variation with depth of salt can also be obtained.