ABSTRACT
The semiarid regions of the world, as delineated on the 1977 Unesco map of World Distribution of Arid Regions, occupy about 40 percent of the arid regions. The semiarid tropics, where sorghum and millet are the dominant crops, is defined by the International Crops Research Institute for the Semi-Arid Tropics in Hyderabad, India as including a much larger area than is shown as semiarid on the Unesco map. In the temperate regions, soils of semiarid climatic zones frequently are calcareous throughout the profile or at all depths below the surface layer. One of the more unusual man-made salinity and wetness problems found in the semiarid regions is that of dryland saline seeps. Plant nutrient deficiencies that are likely to occur when crop production is attempted on semiarid region soils center on nitrogen and phosphorus. Water conservation is the primary need for agricultural production in the semiarid regions.
