Esigenze idriche di Vitis vinifera L. in ambiente caldo-arido

摘要

Many important viticultural areas are located in semiarid environments where mean annual rainfall ranges between 400 and 600 mm, rains are mainly concentrated during tile vine rest period, and vineyard water use is meanly estimated between 500 and 800 mm. The daily vine water use is known to be highly related with the air temperature but, at a greater extent, with the net radiation; moreover, the vineyard water use is affected by other environmental conditions influencing the leaf transpiration, such as the air movement and tile VPD, as well as by several agronomical factors such as the vine density, the training system, the vine age, the floor management, the irrigation frequency and the vine phenological phase. The general decrement of vine water status during the growing season induces both stomatic and non stomatic limitation affecting the leaf gas exchange, the vine nutritional status and the canopy development. In order to estimate the vineyard water use, the evaluation of the water requirement and the crop coefficients has been traditionally done by lysimetry; however, some limits of this method have been pointed out in the '90s, mainly as for studies on woody species. Alternative methods more recently proposed are based on micrometeorological techniques such as Eddy Covariance, which allows the direct measurement of air temperature, water vapour and carbon dioxide, and Surface Renewal, which allows to estimate matter and energy exchange by measuring the air temperature at high frequency. The water deficit, as a limiting factor, is known to affect the canopy development more than the carbohydrate production, thus, when a performing vine leaf area has been already reached, a moderate water deficit may be imposed to reduce the rate of shoot development, and thus the transpiring leaf surface, without compromising the leaf functioning. Many factors concern the estimation of the water requirement in winegrape and tablegrape vineyards and the effect of the irrigation water supply on the berry quality. The main research carried out on this topic pointed out a post-berry set or post-veraison water deficit as the irrigation strategy more helpful to achieve the equilibrium between the vegetative and the reproductive activity and a good berry quality.