Irrigation Strategies Impact Baco noir Grapevines in Ontario. I. Vine Physiology, Vine Size, and Yield Components

Abstract

Irrigation experiments were conducted on the French-American hybrid Baco noir in a vineyard in Virgil, Ontario, Canada, from 2005 to 2007. Effects on vine physiology, shoot growth, and yield components of three regulated deficit irrigation (RDI) levels (100, 50, and 25% crop evapotranspiration [ET_c]) combined in a factorial experiment with three timings of irrigation initiation (fruit set [FS], lag phase [LP], and veraison [VRN]) were compared to a nonirrigated control. The control and late deficits were frequently below wilting point in all seasons and there was substantial variation among treatments in soil water content up to 50 cm deep. Transpiration (E) rates were highest in July and August and dropped by late August. Over the growing season, the control had the lowest E rate while 100% ET_c initiated at FS was highest. In 2005 and 2007, shoot growth rate had almost the same trend: 25% ET_c was slightly greater than the control. Vines irrigated at 100% ET_c imposed at FS had the highest growth rate. Leaf water potential (Ψ) was higher (less negative) in 100% and 50% ET_c compared to the control throughout the growing seasons. Leaf Ψ trended downward at the end of August in all treatments and experimental years. The control had the lowest (most negative) leaf Ψ value in 2007. The control and 100% ET_c initiated at FS did not show differences in all yield components. Trends in yield were not constant across treatments, although RDI treatments showed an increase in some yield components compared to the control. The RDI technique could be a profitable management tool in Ontario vineyards, with positive effects on vine physiology and yield.