Relation between evapotranspiration rate and maize yield

Water use efficiency is evaluated in terms of the ratio of dry matter yield to seasonal evapotranspiration. A 5‐year maize irrigation experiment was conducted in which the root zone soil moisture balance and crop response were measured in relation to potential and actual evapotranspiration. A threshold evapotranspiration of 250–300 mm was indicated below which production was negligible and above which production rose linearly with the amount of water applied. Water use efficiency increased with higher quantities of irrigation provided that soil aeration was not impeded and potential evapotranspiration was not exceeded. It is concluded that a ‘wet’ irrigation regime, permitting the crop to transpire at a rate approaching the climatically induced potential and simultaneously preventing the occurrence of moisture deficits, can help to realize the full productivity of the crop.