ISHS Acta Horticulturae 537: III International Symposium on Irrigation of Horticultural Crops
AN EVAPOTRANSPIRATION MODEL ADAPTED TO WATER STRESSED CROPS |
| Authors: | G. Rana, M. Mastrorilli, N. Katerji |
| Keywords: | Semi-arid climate, canopy resistance, soybean, grain sorghum, sunflower. |
| Abstract:
A method to estimate actual evapotranspiration (ET) at daily scale is presented. It is based on the Penman-Monteith model, in which the canopy resistance (rc) takes into account the plant water status. Since rc cannot be directly measured, it is estimated by existing models. Usually, rc models are either very sophisticated and difficult to apply in practice or too simple and not useful for crops growing under water stress conditions. Here we propose a general version of an ET model at a daily scale, in which the problem of the rc determination is overcome by introducing a daily coefficient which is a function of the pre-dawn leaf water potential (psi.lc.gifb). Since the relationship between psi.lc.gifb and rc does not depend on soil type, such an ET model could be easily used in different environments without a local calibration. The performance of the presented ET model has been tested in three species (soybean, grain sorghum and sunflower) by comparing simulated and measured ET values. The model has been evaluated during summer in open fields, in a site of Southern Italy submitted to the Mediterranean climate and irrigated with two water regimes (optimal and limiting). The Bowen ratio method was used as reference method for monitoring crop ET. For soybeans, a multi-site test was carried out for verifying the model performance at another site (Southern France) without local calibration. The model showed a good performance in estimating ET in both sites and also when the crop was growing under varying conditions of soil water availability. | |
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