- Summer 1995 "Update" Newsletter Article -
Researchers testing new production techniques
Deficit irrigation treatments will be applied under different trellis and pruning systems
From CATI Publication #950701
Copyright © 1995. All rights reserved.
Above average rainfall was welcome to most areas of thirsty San Joaquin Valley farmland this past winter. But as growers are all too aware, future historical records will likely show 1994-95 as simply a blip among rainfall seasons that are typically near desert dry in this productive California growing region.Facing a growing population of thirsty human consumers, the state's farmers must continue seeking ways to improve efficiency in irrigation practices and overall farming methods. Subsurface drip irrigation, or SDI, may be that next level growers need to reach.
SDI has the potential to become "the ultimate" in irrigation systems, observed Keith Striegler, research scientist with California State University, Fresno's Viticulture and Enology Research Center (VERC).
"If managed properly, SDI can provide maximum efficiency for growers," Striegler said in discussing a study in which he is testing the technology in combination with different trellis systems for grapevines.
SDI uses underground tubing to deliver water directly to the plant’s root zone. With no water on the soil surface, none is lost to evaporation or is available to weed seeds.
Striegler's project, supported by the California Agricultural Technology Institute (CATI), is examining combinations of SDI, trellis systems, and deficit irrigation practices to determine which work best in the central San Joaquin Valley.
"This is a major project. Our objective is to find a system that will optimize production in this area," he said.
Different trellis systems, such as the "Geneva double curtain" and "open lyre" already have proven effective for increasing yield in coastal and northern California grape-growing regions. They provide extra trellis wires for training the vines, which can enhance vine growth and fruit yield, the viticultural researcher noted.
However, there’s no guarantee those systems will give larger yields - with quality - in the heat of the San Joaquin Valley. Average inland temperatures range from 15 to 20 degrees warmer than in coastal regions. And greater yield per vine can affect fruit composition, including sugar content, thus reducing quality of raisins, juice concentrate, wine, and other products.
In addition, "T"-shaped trellis systems such as the Geneva double curtain and open lyre are not well-suited to current mechanical harvesting systems, so there are technology issues that still need to be addressed before such systems could be adopted in the San Joaquin Valley, Striegler noted.
Along with the different trellis systems, the project calls for deficit irrigation treatments using 80, 60 and 40 percent of needed application, according to crop evapotranspiration standards. Perhaps a trellis system encouraging more vigorous growth, but with less water applied, would produce higher yield but still with the desired sugar and acid content, Striegler said.
The study is being conducted on a 15-acre vineyard of Sauvignon blanc wine grapes located on the university farm. Cooperating in the project is the university’s Center for Irrigation Technology (CIT), which has overseen installation and operation of the irrigation system (see following article related to SDI and weed growth).
Striegler, with the help of staff researchers and technicians, will collect a variety of data during the course of the multi-year study, including measurements of vine transpiration, nutrition, canopy microclimate, yield, wine composition, and pruning weights.
"Clearly, there is a lot of benefit potential in subsurface drip irrigation. It could be the ultimate system if managed properly," he said.
Results from the study will be presented, as they become available, in various conference and seminar formats, and in CATI publications. For more information on this project, Striegler may be contacted through VERC at (559) 278-2089.
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