AHUJA L. R.Soil Science: November 1974 Original Article: PDF Only Buy Abstract Applicability of the Green-Ampt approach to describe water infiltration through surface crust after the rapid initial stage is evaluated by testing the equations of Hillel and Gardner (1970) and two modifications of these against numerical-solution data for Yolo soil. The modifications were designed to approximately account for the transient nature of soil-water content at the crust-soil boundary. One of the modifications involved piece-wise application of Hillel and Gardner's (1970) equations, and the other treated the boundary water content as a continuous variable. The results of tests showed that the unmodified equations of Hillel and Gardner (1970) were fairly good for a smaller crust resistance but involved considerable error for a larger resistance. Piecewise application of these equations with as small as four subranges gave results in close agreement with the numerical solution for both resistances. The other modifications involving continuously variable boundary water content showed very good agreement for both resistances in early stages. In the intermediate stages, it showed errors of large relative magnitude, which decreased with increase in resistance. © Williams & Wilkins 1974. All Rights Reserved.