|
 |
A research team from the
Viticulture and Enology Research Center (VERC) at California State
University, Fresno has joined with an international agricultural
equipment manufacturing company to improve mechanized pruning for wine
grapes in California’s San Joaquin Valley.
Leading the project is assistant professor Kaan Kurtural, who holds the
Bronco Wine Co. Viticulture Chair at VERC and the university’s
Department of Viticulture and Enology.
“As hand labor is becoming more expensive and scarce in the Central
Valley, growers are turning more towards mechanization to reduce costs
and to increase efficiency and sustain-ability of their wine grape
operations,” Kurtural said in outlining the research.
Mechanized pruning of wine grapes is not new, having been introduced in
California more than 10 years ago, Kurtural noted. But manufacturers
have focused mainly on equipment for high quality wine grapes grown on
vertically-shoot-positioned or lyre trellis systems in areas such as the
Central Coast.
More recently, companies such as Oxbo International have developed and
refined systems designed not only for pruning, but also for shoot and
cluster thinning. Key objectives of the current partnership is to test
mechanical systems for shoot and cluster thinning on the type of trellis
system most commonly found in San Joaquin Valley wine grape vineyards –
the California “T,” also known as the California Sprawl.
“The majority of the wine grape acreage in the valley is trained to the
California Sprawl due to its initial low cost of installation,” Kurtural
said. Growers who have tried to adapt existing mechanized pruning
equipment to that system have encountered an assortment of problems
because of the way the vines grow along that type of canopy, however.
Problems include over-shading of clusters, non-uniform shoot and fruit
distribution, uneven fruit ripening, delayed flavor development and
over-cropping.
“If we are to remain competitive in the domestic and international wine
market, the adoption of mechanical canopy management needs to increase
from its current level of 15 percent across California,” Kurtural said.
For this project, the research team is evaluating new mechanical
pruning, shoot thinning and cluster thinning machine heads that Oxbo has
designed for use on the California Sprawl. The project will feature
three treatments: conventional hand pruning and thinning, mechanical
pre-pruning followed by hand pruning and thinning, and mechanized
pruning and thinning.
Last summer was the first season of the four-year project, and results
look promising, Kurtural said.
“We saved close to a quarter per vine in costs, and we did not lose
anything in yield or quality,” he said. At 21 cents per vine, 600 vines
per acre, that amounts to $126 per-acre savings using a completely
mechanized system.
The study is being conducted on Fresno State’s university farm on
Cabernet Sauvignon grapes on Freedom rootstock. The vines are trained to
a bilateral cordon at 54 inches height with a foliage support wire at 66
inches on a two-wire vertical trellis.
Treatment analysis includes measurement of fruit yield, cluster numbers,
average berry size, percent total soluble solids, juice pH, titratable
acidity, and anthocyanin and phenolic concentrations. Crop load and leaf
area to fruit ratio also will be calculated based on yield and pruning
weight per vine.
Confirmation of the positive results over several years of study “would
have the potential for having a relatively rapid impact on grape and
wine industries in the San Joaquin Valley,” Kurtural said.
Assisting in the project for Oxbo is viticulturist Greg Berg, working
out of the company’s Kingsburg sales and service office. Oxbo, which has
manufacturing plants in Washington and Wisconsin, has provided funding
to help fund the research as well as engineering expertise in the
development of custom pruning and thinning heads. Also supporting the
research is Bronco Wine Co.
For details on this project, contact Kurtural at
kkurtural@csufresno.edu.
(Copy by Steve Olson of
the California Agricultural Technology Institute.)
|
