Evapotranspiration and crop coefficients from lysimeter measurements of mature ‘Tempranillo’ wine grapes

Vineyard irrigation management based on knowledge of the crop water requirements, is critical in the semi-arid zones for improving fruit quality and production stability as prerequisites for obtaining wines of high quality. The aim of this study was to quantify the water use of a mature Vitis vinifera cv. Tempranillo vineyard grown for wine production without soil water limitations during three growing seasons (2007–2009). The experimental work was carried out in the lysimeter facilities located in Albacete (Central Spain). In 1999, a weighing lysimeter with an overall resolution of 250 g was installed in the center of a vineyard (100 m × 100 m). A monolith of undisturbed soil was placed inside the lysimeter tank, which was 3 m × 3 m and 1.7 m deep. Two vines under drip irrigation were planted in the lysimeter, each one occupying 4.5 m2, the same area as the vines in the rest of the plot. To schedule irrigation, ETc values were calculated from daily mass loss minus drainage loss, and water was applied to replace the loss, thus, maintaining non-limiting soil water conditions. Seasonal grapevine evapotranspiration (ET) measured in the lysimeter was 550 mm in 2007, 377 mm in 2008 and 505 mm in 2009. The lower ETc values in 2008 were directly related to a smaller canopy in that year caused by a late frost. In the three study years, maximum average Kc values reached values of approximately 0.75, 0.60 and 0.70, respectively from veraison to harvest and were related to maximum canopy cover values of 45, 33 and 40 percent, respectively. The dual crop coefficient approach was used to separate crop transpiration (Kcb) from soil evaporation (Ke). As canopy increased, Kcb values increased and Ke values decreased from veraison to harvest stage. Linear relationships were found between the lysimeter Kcb and the canopy cover (CC) for the three seasons, and a single relationship that related Kcb to growing degree-days (GDD) was established (Kcb = 0.0004 × GDD + 0.093; R2 = 0.97) allowing extrapolation of our results to other areas.