Grapevine Response to Irrigation and Trellis Treatments in the Salinas Valley

Abstract

Four irrigation treatments (nonirrigation, early cut off, early cut back and late cut off) each with three trellis types (2-wire vertical, 1.4 m high; 3-wire vertical, 1.7 m high; and 2-wire vertical, 1.7 m high with a 0.6-m cross-arm were tested to determine effects on the yield and growth of Cabernet Sauvignon and on the composition of the fruit. The split-split-plot experiment was conducted in a low rainfall Mediterranean climate near Soledad in the Salinas Valley of Monterey County, California. The soils were classified by the Soil Conservation Service as a Chualar loam. Topsoil and root depth was uniformly shallow, approximating 50 cm. Irrigations were scheduled primarily on the basis of tensiometer instruments 40 cm deep. Soil suctions in the irrigated plots were maintained between 10-30 cb during the early season until vine growth resulted in uniform canopy density down the vine row with some shoots trailing the ground. Irrigation then was discontinued for the early cut off treatment; soil suctions were allowed to approach or exceed 80 cb for the early cut back treatment before subsequent irrigations in order to retard further shoot growth; but suctions ranging between 10-50 cb were maintained for the late cut off treatment through mid-September. A soil moisture tension of 1-7 bars at harvest was the goal for the last two treatments.

Statistical analysis showed significant differences in °Brix, total acidity, pH, yield of both grapes and fruit sugars, cluster numbers and weights, berry weights, bloom-time petiole percentages of Na, K, and Mg, harvest-time must levels of arginine, and pruning weights.

The late cut off treatment showed delayed maturity and lower yields than the early cut back treatment. The non irrigated and early cut off treatment did not result in a more favorable sugar, acid and pH balance, and resulted in lower yields than the early cut back treatment. The 2 wire vertical trellis with a cross-arm resulted in higher yields than the other two trellises only for the early cut back and late cut off irrigation treatments receiving pre-harvest irrigations.