A research team from the Viticulture and Enology Research Center (VERC) at California State University, Fresno has joined with an international agricultural equipment maker to improve mechanized pruning for winegrapes in the San Joaquin Valley.
“As hand labor is becoming more expensive and scarce in the Central Valley, growers are turning more toward mechanization to reduce costs and to increase efficiency and sustainability of their winegrape operations,” says the project leader, Kaan Kurtural, an assistant professor who holds the Bronco Wine Co. viticulture chair at VERC and the university’s Department of Viticulture and Enology.
Mechanized pruning of winegrapes is not new, having been introduced in California more than 10 years ago, Kurtural told the Central Valley Business News. But manufacturers have focused mainly on equipment for high quality winegrapes 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. A key objective 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 winegrape vineyards — the California “T” — also known somewhat less elegantly as the “California Sprawl.”
“The majority of the winegrape acreage in the valley is trained to the California Sprawl due to its initial low cost of installation,” says Kurtural. 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 concludes.