ABSTRACT
Cotton is the most important fiber plant in agriculture. In 1980 the areas of the world planted with this crop covered 33 million ha, or 82,500,000 acres. These areas range from 42° N to 35° S latitude, wherever the temperature is adequate (see Figure 1). Most of the cotton is rain fed and only a small portion is irrigated. In the arid zones where the rain is insufficient, less than 250 mm/year, cotton is grown under full irrigation. Under correct irrigation the yields may reach higher levels, because it is possible to provide optimum moisture conditions in the soil. The less the natural precipitation during the growing season, the greater is the possible control of the moisture regime by means of irrigation. This advantage may result in yields which fully offset the cost of irrigation. It may be expected, therefore, that an increasing proportion of the cotton grown in the world will be based upon irrigation. Irrigation must, however, be accompanied by carefully designed measures for water management, drainage, and control of soil salinity.
