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Evaluation of deficit irrigation strategies for Vitis labruscana 'Concord' in central Washington

Stout, J. E., Davenport, J. R.
Acta horticulturae 2017 no.1150 pp. 435-442
Vitis labrusca, climate, deficit irrigation, evapotranspiration, fruit quality, grapes, growers, irrigation management, steppes, vines, Washington (state)
The semi-arid steppe climate in central Washington necessitates irrigation of Vitis labruscana 'Concord' grapes to maintain production. However, many growers in this area overwater their vines. Our project evaluated the effects of several levels of regulated deficit irrigation (RDI) on yield and fruit quality in 'Concord' grape (CG) vines. The CG treatments were limited to between bloom and veraison in order to minimize impacts on future crop potential and were based on crop evapotranspiration (ETc). The treatments were divided into relative rates of water application: high (current grower practice), moderate, low, and very low. These roughly corresponded to reductions of 35, 45, and 60% from the grower control. Parameters measured were shoot length, yield and fruit quality. Harvest data indicated severe decreases in yield in 2012 continuing through 2013 except for the moderate treatment, which recovered in 2013 matching the yield of the control. In 2014, both the moderate and low treatments yielded within 1 Mg ha-1 of the control treatment. This recovery in yield could be a result of changes in the root distribution that took place over the previous 2-3 years allowing the vines to adapt to the decrease in wetted area over the season.