Subsoil Tillage as an Aid in the Reclamation of the soils in the Casa Grande Series in Arizona

Abstract

Sixteen per cent or 91,520 acres of soil in the Casa Grande Valley in South Central Arizona consists of soils belonging to the Casa Grande series. Until recently, these soils have not been highly productive because of physical condition and the presence of alkali and salts. The Casa Grande soils are classed as being saline-alkali. They are described, in part, in the soil survey report4 of the area as follows: " They are highly alkaline, contain sodium saturated clayt, which is dispersed and tough, and are unfavourable, both chemically and physically, for the growth of plants. The barren slick spot — soils are dense and ex- clude both air and water to a great extent. They become baked, hard, and difficult to till when dry and are so plastic and sticky when wet that they cannot be ploughed or cultivated satisfactorily." The profile characteristics of these soils became known through a soil survey report by Poulson, Wildermuth, and Harper' who were the first to recommend deep tillage as a desirable soil management practice. They showed that the Casa Grande series exhibits a relatively heavy surface soil underlain by a relatively sandy horizon found at depths varying from 18 to 32 inches below the surface. The surface soils being dispersed did not permit water to enter the soil to leach away the excess salts or to furnish moisture for plant growth. As a result, water in quantity seldom entered the more permeable sandy subsoils. The object of deep tillage was to break up the surface and to open the subsurface and substratum layers to water.