Crop water requirements: Insight Features
2001
Steduto, P. (Centre International de Hautes Etudes Agronomiques Méditerranéennes, Bari (Italy). Institut Agronomique Méditerranéen)
The determination of the crop water requirements (ETc), under irrigated agriculture, still relies on the so-called "two-step" approach. The 1st step consists in deriving the evapotranspiration of a reference crop (ET0) and the 2nd step consists in utilizing a crop coefficient (Kc) which is supposed to account for the specific crop, stage of development, conditions soil surface wetness and interaction crop-atmosphere, so that ETc is the product of such two parameters: ET0 and Kc. This approach has shown to be robust, practical and effective, but also be prone to some significant uncertainties in its application, particularly the Mediterranean Region. In this paper, then, some of the most relevant issues for the correct determination of crop water requirements are discussed in order to highlight the related risks of errors. The discussion, developed both on the theoretica1 and practical grounds, will concern: the influence of the soil wetness when ground-cover by the crop canopy is incomplete (the evaporation component of the evapotranspiration process); the impact of macro- advection on ET0 and Kc; the way the crop coefficients (Kc) are derived; the problems encountered when working on tree crops, etc. All these aspects deserve special consideration when operating in arid and semi-arid environments of the Mediterranean Region.
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