Cover crop influence on water relations, yield, grape and wine composition of Pinot noir

The effect of cover crop on the water relations, yield and grape composition of Pinot noir vines was investigated during two seasons (2003 and 2004) in a gravely soil located in Tarragona (Spain). Seventeen-year-old vines, grafted onto R110 and trained onto a Ballerina training system, were used. Treatments (Rye grass and a clean tillage control) were replicated four times in a block layout. Leaf water potential was measured during mid-day at pea size, véraison and ripeness stages. Berry composition was determined at ripeness. At harvest, yield components were determined and one wine made per treatment. Severe water stress occurred in 2003, which resulted in the grass cover treatment producing less leaf area per vine and a reduction in leaf water potential during the day. However, in 2004, significant differences occurred only at 8:00. The same pattern was observed for berry weight and the yield parameters; they were lower in 2003 with cover grass. The anthocyanin content, total soluble solids and titratable acidity decreased strongly after véraison, only in 2003. Grass cover had a negative effect on total phenol and alcohol contents of wines in the extremely dry year. Contrasting effects were found in 2004.