Interactive Effects of Irrigation and Crop Level on Tempranillo Vines in a Semiarid Climate

The effects of different irrigation and crop level regimes on performance of Tempranillo vines in a Mediterranean climate were studied under field conditions over a 4-year period (2005 to 2008). Vines were subjected to irrigation treatments that provided 100, 50, or 25% of crop evapotranspiration (ETc) or to a dry-farmed regime. Two crop levels (high and low) established by veraison cluster thinning were studied for each of the treatments. Increased irrigation doses resulted in higher yield and vine growth, although the 25% ETc treatment showed the highest irrigation water use efficiency, with yields similar to the 50% ETc treatment. The short-and long-term (next crop season) effects of the treatments on vegetative and productive parameters (i.e., leaf area index and cluster weight) were related to vine water status, especially in relation to the preveraison period. Irrigation increased must titratable acidity (TA) but did not affect total soluble solids or pH. Cluster thinning resulted in a higher leaf area-to-yield ratio and lower yield even though a compensatory increase in cluster weight was observed in the low crop level treatments. For similar Brix, cluster thinning decreased TA and increased must pH, a negative result because must pH values in the study region are generally too high. Irrigation at 25% of ETc can be considered a good strategy for increasing yield compared to dry-farmed vines while also maximizing water use efficiency without compromising grape composition.