The reaction of vineyards to fertilizer inputs is highly dependent on irrigation management in irrigated areas and the two inputs cannot be separated from a management point of view.
As a result of their sensitivity to moisture stress, more than 80% of plantings in South Africa are currently irrigated. If one considers that close to 50 000 ha of potatoes are planted in this country, one cannot but realise that the potato industry is a major consumer of water.
The water use efficiency (WUE) of a grain crop is a measure of how much grain is produced by a crop for each millimetre of effective rainfall and is usually expressed as kg of grain produced per hectare per mm of rainfall (kg/ha/mm).
Global demand and consumption of agricultural crops for food, feed and fuel is increasing at a rapid pace. To satisfy the growing, worldwide demand for grain, two broad options are available.