- Winter 1997 "Update" Newsletter Article -
Cover crop trials bring ample yields
From CATI Publication #970101
Copyright © 1997. All rights reserved.
A three-year study at Fresno State has shown grapevines maintained with cover crops and compost can produce yields nearly as great as vines managed by "conventional" practices.
The trials were conducted in a Thompson Seedless vine yard on the University Farm, with data analysis and conclusions compiled in a publication now available from the California Agricultural Technology Institute (CATI). Primary authors are Keith Striegler, research scientist with CATI's Viticulture and Enology Research Center (VERC), and Mark Mayse, professor of entomology in Department of Plant Science. Objectives of the study were to determine the effects of nitrogen fertilization practices and cover crops on growth, yield, selected arthropod densities, and other viticultural characteristics in a central San Joaquin Valley vineyard.
Treatments included conventional cultivation of row middles and application of synthetic nitrogen fertilizer. "Sustainable" methods featured the use of cover crops instead of cultivation, and compost rather than synthetic nitrogen.
Yield results varied over the three years of data collection, with conventional practices producing the highest average yields nearly as high as those receiving conventional.
Although no formal "cause and effect" conclusions can be made about sustainable practices and yield at this time, there are correlations that can be drawn, Mayse noted. For example, cover crops often increase irrigation efficiency by making the soil more penetrable. Compost promotes microbial development in the soil , enriching it with a broader range of chemicals. Both of these factors tend to improve vine health.
And cover crops can also help reduce the numbers of destructive pests such as the variegated leafhopper (VLH) and the western grape leaf hopper (WGLH). During the third year of the study, for example, higher counts of predatory lacewing larvae, a beneficial insect, were noted in the vineyard areas with cover crops. Along with this were lower counts of WGLH.
Conventional cultivating and synthetic nitrogen application can "pump up" the vine and lead to high production. But sustainable practices, once established in the vineyard, can promote healthier vines - better able to resist the effects of pests and disease - and also capable of producing good yields, the authors conclude in their report.
Title of the authors' new report is "Response of Thompson Seedless Grapevines to Sustainable Viticultural Practices." Single copies are available from CATI at no charge. Copies are available and may be viewed or requested from the Research Publications page.
For more information about the authors or their work, call VERC at (559) 278-5680, or visit the VERC World Wide Web site at http://cati.csufresno.edu/verc.{ page top }