Susceptibility of wheat to water deficit at three growth stages

The grain yield of wheat (Triticum aestivum L.) to different water deficit levels at three stages of growth was obtained from field measurements conducted at the Aahmadu Bello University Farm, Samaru-Zaria. Also, the suitability of a time-based characterisation of water deficit for crop susceptibility determination was tested against a plant-based one. The plant-based measure of crop water stress, as caused by water deficit, was calculated as the product of relative evapotranspiration deficit and the duration. The crop susceptibility was the relative grain yield reduction due to a given crop water stress. The results showed that the level of water deficit determines the relative crop susceptibilities to water stress for the crop growth stages considered. Also, the relationship between time intervals (irrigation frequency as a measure of water deficit) and a plant-based water deficit varied during the crop growth season. Thus, the sole use of a time-based characterisation of water deficit for the determination of crop susceptibilities at defined growth stages is found to be unsuitable. However, since the local farmers may find it difficult to use the more sophisticated plant-based water deficit characterisation, a relationship between the plant-based and time-based water deficit characterisation for the different crop growth stages was established. Therefore, the plant-based water deficit characterisation can easily be estimated using the established relationship and the appropriate irrigation scheduling determined.