膜孔肥液自由入渗土壤水氮运移转化的数值模拟

Numerical simulation of transport and transform of soil moisture and nitrogen under film hole infiltration with fertilizer

本文根据土壤水动力学方程和溶质运移理论,考虑了土壤氮素的挥发、吸附、硝化、反硝化和矿化作用等动力学过程,而忽略作物根系对土壤水分和氮素吸收过程,建立了膜孔肥液自由入渗土壤水氮运移转化的数学模型,运用试验资料确定与模型相关的土壤水分及土壤硝态氮和土壤铵态氮的参数,利用ADI格式结合Gauess-Seidel迭代法对方程进行求解。结果表明:土壤含水率和土壤铵态氮以膜孔为中心沿水平方向和垂直方向逐渐减小,而土壤硝态氮先增大后减小。随分布和运移转化时间的增大土壤含水率和土壤铵态氮逐渐减小,土壤硝态氮逐渐增大。土壤含水率及土壤硝态氮和土壤铵态氮实测值与计算值根方误差的平均值分别为0.7444、0.6518和0.8300,吻合良好,具有变化规律的一致性,则该模型可以反映膜孔肥液自由入渗土壤水氮运移转化规律。

A mathematical model was developed to simulate the transport and transform of soil moisture and nitrogen under film hole infiltration with fertilizer using the soil water dynamics equation and soil solute transport theory. This model neglects the root＇ s absorption of soil moisture and nitrogen and focuses on the dynamics process of volatilization, adsorption, nitration, denitrification and mineralization of soil moisture and nitrogen. It was solved with an ADI seheme and Gauess-Seidel iteration method, and its parameters were verified with experimental data. The results show that soil moisture and NH4-N content decrease gradually with depth and with horizontal distance to the film hole while NO3-N content first increases and then decreases in these two directions. With the elapse of transport and transform time, soil moisture and NH4＋-N content decrease while NO3-N content increases. The calculated values and trends agree well with measurements. The average errors of calculated soil moisture, NO3-N content and NH4^＋ -N content are 0. 7444,0. 6518 and 0. 8300 respectively.