Irrigated area accounts for 55% of world cotton area and the remaining 45% is rainfed ("dryland"). The cotton plant needs water in order to incorporate nutrients and offset water losses from evapo-transpiration. Insufficient ground moisture affects cotton yields. If irrigation is not available, rains can provide for water needs of the plant. However, under rainfed conditions, the moment and duration of rains cannot be planned. Besides irrigation, other factors that affect cotton yields include soil quality, variety, seed quality, weather, pesticide and fertilizer use, and crop management. However, all these factors being equal, irrigated yields are usually higher than rainfed yields because of the ability under irrigated conditions to time input applications.
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