WATER QUANTITY

1. Generalized recommendations are available for most crops on the amount of irrigation water to apply and the frequency of application, but these are dependent on local soil type, weather conditions and cost-benefit analysis.
2. A rough guide to the water need of a crop at each stage of its development is to irrigate as soon as wilting or other indicators of stress are observed (the amount applied being determined on the basis of previous year's experience), and to repeat the process until the signs of stress disappear.
3. A more accurate approach is to measure rainfall and evapo-transpiration rate and to calculate soil-water deficit and irrigation need through the growing season, but this is a complex and costly procedure which is feasible only for large-scale irrigation companies.

Related information: Other factors in Irrigation management: water quality: water application; drainage method; water charges; irrigation management.