- Timing of water delivery
- Amount of water available
- Duration, intensity, and timing of hot spells
- Soil texture
- Soil depth
- Method of irrigation
In newly planted vineyards, water management is critical for proper vine establishment. Without sufficient root growth, which is driven by the supply of adequate moisture, vines will struggle with establishment and winter survival. Under drought advisories, if water restrictions are substantial enough to prevent proper irrigation regimes, growers may consider delaying the establishment of new vineyards until irrigation forecasts have improved.
The information presented here, along with other advisories on irrigation management and efficiency, outline the management concerns and possible solutions for growers during periods of inadequate water availability for mature plantings.
Grapevine Water Use
Grapevines can adapt to both low and high water availability in the surrounding soil. Vitis labrusca ‘Concord’ is native to the eastern United States and is thus more suited to higher water availability. Wine grapes (Vitis vinifera) have evolved under drier conditions and are more efficient in their water use.
Regardless of plant origin, a basic volume of water is needed for vine survival; in order to reach optimum yield and crop quality, more water than the “absolute minimum” is needed. A general rule of thumb is that 12-16 acre-inches of water is the minimum amount required during the growing season to actually produce a viable crop. However, this rule is highly variable because it is affected by soil type, age of vine, weather, root depth, crop load, and other growing attributes. This effectively means that vines can survive droughts, depending on the severity and duration of the drought, but they may not produce fruit.
Effects of Water Stress
Extreme water stress in vines is most damaging when it occurs between the phenological stages of bloom to pea-size berries (late spring to early summer), concurrent with rapid shoot growth, ovule fertilization, and rapid cell division in young berries (Figure 1). Water stress during this time will result in poor berry set and small berries.
Between the stage of véraison and harvest, RDI is still a common practice in red wine grapes, but not white wine grapes or juice grapes.
At this time, vines are less susceptible to drought conditions because they begin using the phloem, rather than the xylem, for water transport. The phloem is less susceptible to changes in soil water levels (Keller 2010); however, they still need sufficient soil moisture so as not to go past the permanent wilting point of the plant. RDI during this time period aids in slowing vegetative vine growth, and helps the processes associated with vine dormancy and cold hardiness acclimation.