Modeling Soil Water Movement for Trickle Irrigation.

摘要

Solutions of the time dependent linearized soil moisture flow equation have been completed for point,line,strip,disc and ring sources. These solutions were used to simulate time dependent moisture regimes for various geometries used in trickle irrigation. They are also useful as a check for elaborate finite difference or finite element schemes for solving the non-linear moisture flow equations. For one-dimensional steady state flow,analytical solutions were obtained for seven types of plant water withdrawal functions depending on the flux potential as well as the depth below the surface. The solution of the linearized moisture flow equations with a point source has been compared with the finite difference solution of the non-linear equations of Brandt et al as well as with field data measured on sandy soil in Yuma and the Sinai. These comparisons were very favorable but demonstrated that care must be taken in applying the model to problems involving large fluxuations in moisture content. Two field experiments for measuring evapotranspiration under trickle irrigation were made in citrus groves near Yuma. The objectives of these measurements were to study the water uptake distribution in the close vicinity of a tree and the microclimate of a grove under trickle irrigation.