Transpiration and evaporation of grapevine, two components related to irrigation strategy

The quantification of evaporation is crucial for the appropriate use of water, especially in arid areas where rainfall is scarce. An experiment was carried out in a semiarid area of Spain (Albacete) with the objective of quantifying the evaporation and transpiration of grapevine cv. Tempranillo and the effects of irrigation frequency on the evaporation. Measurements of transpiration and crop evapotranspiration of grapevine cv. Tempranillo without soil water limitations were conducted in a weighing lysimeter covered with a waterproof canvas during different periods from 2011 to 2014. The transpiration rates measured on the days after irrigation were higher than those measured when irrigation was not applied or when there were no precipitation events. Evaporation, calculated as the difference between the days on which the lysimeter surface was covered or not covered, ranged from 81% of evapotranspiration in the first phenological stages to 30% close to the time of full canopy cover. Under similar canopy cover and reference evapotranspiration, transpiration measured on the days when irrigation was applied was greater than transpiration measured on the days when the vines were not irrigated. Different irrigation strategies were applied to determine the effect of the quantity of water applied on the evaporation, and the results showed that the greater the amount of irrigation applied, the higher the efficiency, when the irrigation frequency is reduced; in fact, three times more water was applied during each irrigation event and the evaporation percentage was 7% lower. Therefore, a high irrigation frequency should be questioned in semiarid areas.