"The concept is known as deficit irrigation. You give the vines less than 100 percent of their actual water needs prior to veraison, or ripening," said Ed Hellman, Texas Cooperative Extension viticulture specialiast based in Lubbock. Hellman has a joint appointment with Texas A&M University and Texas Tech University.
"Deficit irrigation uses less water. When done correctly, it also influences the amount of canopy the vines produce."
A small canopy has several advantages. Vines require less water throughout the growing season. More sunlight reaches present and future cane buds, where vines flower and set grapes. Sunlight, in turn, promotes fruit quality of ripening grapes.
A small canopy requires less annual pruning and allows more air circulation in the vines, which reduces the potential for plant disease. Regulating irrigation prior to ripening may also promote cold-hardiness of canes that produce fruiting buds.
"There are more than 3,000 acres of wine grapes in Texas, but there has been little research aimed at generating irrigation guidelines," Hellman said. "Deficit irrigation is a new concept in Texas. It shows promise, but it will probably only work in low rainfall areas such as West Texas where most of the plants' water needs are met by irrigation."
Hellman and research associate Ashley Basinger began evaluating regulated deficit irrigation at the Newsom Vineyard near Plains, Texas, in 2002. Their research is part of Basinger's graduate studies towards a master's degree at Texas Tech University. They also tried a deficit irrigation strategy known as partial root zone drying, which originated in Australia. With partial root zone drying, irrigation water is alternately applied to only one-half of a vine's roots.
"We tested regulated defi
Contact: Tim W. McAlavy
Texas A&M University - Agricultural Communications