COVER CROP MANAGEMENT IN VINEYARDS TO ENHANCE DEFICIT IRRIGATION IN A HUMID CLIMATE

In 1991, we established the three vineyard floor management treatments of bare soil, rye grass sward, and chicory sward in the inter-row. These were combined with two irrigation regimes of standard and deficit irrigated in an 11-year old irrigated Sauvignon blanc vineyard to reduce vine vigour. There were no differences in vine vigour between the treatments in the first year. From the second to the fifth year, rye grass and chicory swards reduced the weights of summer trimmings and winter prunings up to 80 % compared to bare soil. This reduction in vegetative vigour was attributed to significantly lower soil moisture beneath rye grass and chicory swards compared to bare soil. In the berries, titratable acidity was higher whilst soluble solids concentration and sugar/acid ratio were lower from the bare soil than either the chicory or rye grass treatments. Differences were significant only in the third year. Floor management has not affected the total yield in the first five years of the trial. Deficit irrigation reduced titratable acidity and increased the sugar/acid ratio in the second year compared to standard irrigation. Over five years, total yield was 6% higher with standard irrigation. However, significant differences in yield were found in year three only.