Soil Survey for Irrigation

Abstract

Soils are three-dimensional bodies. They have profiles, consisting of specific kinds and combinations of horizons, as well as specific surfaces and relief or landscape features. They are formed by a combination of natural processes under the interrelated influence of climate, vegetation, relief (including hydrology), parent material, and time. In the drier areas of the world—the arid, semiarid, and subhumid zones—soil productivity is usually limited by lack of water. Therefore, if sustained agricultural production with satisfactory yields is desired, irrigation must supplement the natural water supply. The quantity of water to be applied, as well as the frequency and the techniques used in its application, depend on the nature of the soils, as well as on the prevailing climate and the system of agriculture. Furthermore, in most dry areas, water is a scarce commodity. Also, its quality, in terms of contents of salt and silt, is very variable. The kind and amount of water applied not only influence the yields of the crop, but also modify the properties of the soils, and this may essentially affect productivity in later years. Some problems may be partially overcome by a drainage system to leach excess salts. A soil’s suitability for irrigation therefore cannot be assessed without due attention to its suitability for drainage.