Principles of water management under drought conditions

Abstract

In rain-fed agriculture the options for water management are much more limited than for irrigated agriculture and the management rools available to the farmer are few. The major variable at his disposal is the selection of the crop to be grown. The economic return per unit of water is the major factor to be considered. This usually implies the maximum possible ratio of grain or other harvested plant part to total dry matter. When the rainfall is just below amount needed for maximum dry matter production, this maximum can be achieved through appropriate manipulation of the plant population. The optimum population depends both upon the characteristics of the plant and the amount and distribution of the precipitation. When the amount of precipitation is significantly less than about 25% of the optimum, then other management approaches are required. A widespread solution to this problem has been summer-fallowing. However, in certain circumstances some variation on surface water management or water harvesting may be more advantageous. Criteria for decision making for optimum production under dry-land conditions are given.