- Spring 1999 "Update" Newsletter Article -
Repot reveals San Joaquin Valley yields for red cultivars
Copyright © 1999. All rights reserved.
Increased consumer demand for premium red wines has prompted California grape growers to plant more of the prized red varieties. Acreage of cultivars such as Cabernet Sauvignon, Merlot and Syrah have been expanding rapidly during the last five years.
However, most of those plantings have taken place in the milder grape-growing regions of California, such as the central coast, northern San Joaquin Valley and Napa-Sonoma regions. The San Joaquin Valley has generally proven to be too hot for the red varieties to flourish.
However, research work at California State University, Fresno may offer new opportunities for growers by revealing the viability of certain red cultivars under specialized viticulture practices. A brief report just published by the California Agricultural Technology Institute (CATI) provides initial data from this research. The report is titled "Evaluation of Cultivar and Canopy Management Practices for Wine Grape Production in the Southern San Joaquin Valley." Authors are graduate student researcher Jon Affonso and former research scientist Keith Striegler. The work is being conducted through the Viticulture and Enology Research Center (VERC).
The cultivar research project began several years ago with the grafting of six different red cultivars onto common Harmony rootstocks at Fresno State's University Farm. The cultivars are Syrah, Sangiovese, Cabernet Sauvignon, Zinfandel, Barbera and Merlot.
In overall yield comparisons from the 1996-97 growing season, the Barbera block out-produced all others by a considerable margin, yielding the equivalent of 14.3 tons per acre. The Syrah and Sangiovese varieties followed, each yielding approximately 11.5 tons per acre.
The Cabernet Sauvignon produced a "good" yield equivalent of nine tons per acre, and the Merlot and Zinfandel each produced about seven tons per acre. The Zinfandel was hindered by a summer bunch rot pathogen, the researchers noted.
In another phase of the project, experimental plots were treated with different canopy management techniques to determine which treatment produced the most beneficial results. The treatments included shoot thinning, leaf removal, and a combination of the two. Analysis revealed that shoot thinning reduced yield and clusters per vine while it increased the cluster weight and berries per cluster.
Complete details from the study are available in the report, which can be viewed on the VERC web site at cati.csufresno.edu/verc. Hard copies may be ordered using the Publications Available form on Page 7.
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