Soil erosion on irrigated lands

Abstract

Erosion on the upper portion and sedimentation on the lower portion\nof fields redistributes topsoil. The results of these processes become visible\nwhen the color of the subsoil differs from that of the topsoil (Fig. 37-1).\nThe visual evidence of topsoil redistribution would be lacking where subsoil\nand topsoil are nearly the same color. Furrow erosion can cause a major\ntopsoil redistribution on any field and have a simultaneous, severe, negative\nimpact on crop production.\nTypical fields that have been irrigated for about 80 yr are illustrated\nin Fig. 37-1, showing the color change as whitish subsoil is mixed with darker_\ntopsoil. The topsoil distribution varies depending upon the field length and\nirrigation practice used over the 80 yr. The deepest topsoil areas, resulting\nfrom deposition, vary from field to field from about the midpoint to the\nextreme lower end. Also, there has been a net topsoil loss from most fields,\nthereby negatively impacting crop yield.