Young Grape Vines and Drought

By Rebecca Shortt, Irrigation Engineer (OMAFRA)

Young vines are at greater risk during drought because of their small and shallow root system. Mature vines, have deeper root systems which are better able to access moisture.

In the heat of 2020 what can we do to promote growth?  Keep cover crop mowed short and the herbicide strip free of weeds and well maintained.

Good soil health is a long term strategy that will benefit vines during establishment and also throughout production years.  Employ practices that increase organic matter such as reduced tillage, cover crops and adding manure or other organic amendments.  Tile drainage is necessary to ensure vines establish deep root systems.

Irrigation is key for keeping young vines alive.  Drip irrigation is an excellent practice for all vineyards but especially for young vines where we want to target the water application to the small root area of these new plantings.  Young vines should be fully irrigated until bearing year to promote root growth and above ground growth.

Irrigation of Young Vines:

• Ensures survival
• Increases winter hardiness (increases vine vigour)
• Reduces the number of years till maturity
• Reduces pest problems (erineum mite and European spider mite)

No Irrigation System:

It is very difficult to get enough water by truck (with water tank) for the whole vineyard so I suggest focusing on priority fields.  Newly planted fields are at greatest risk.

Water Needs for Young Vines

Water needs for the vine will depend on the weather.  Newly planted vines (as shown in this photo) will transpire 0.5L to 1 L water per day in the hot weeks of an Ontario summer.  My recommendation is to water 2 L per vine every other day.  Alternatively, 3 to 4L per vine every 3 to 5 days.  If larger volumes are applied, it will soak into the soil outside of the plant root zone.  Using a 775L tank you could water 385 vines with every truck load. The key to watering young vines is to provide enough water to the vine without making the soil overly muddy. Allow the roots to dry out between applications, as this will promote root growth and encourage the vine to put their roots deeper into the soil to access moisture. Excess moisture can also cause issues with root rots. When evaluating water stress in young vines examine the tendrils of the vine shoot. If the tendril extends further than the shoot’s growing tip, the vine has adequate moisture. If the tendrils are shrinking back behind the growing tip, the vine is experiencing water-deficit stress. Remember that “hot water treated” vines will show signs of drought stress before untreated vines. If the vines have not received any significant rainfall (13 to 25 mm or 0.5”-1.0”) within one week after planting they should be watered. Decrease or stop watering the vines in early September to help the vine acclimate for winter.

Drip Irrigation System:

With a drip system I recommend applying 0.8 L/day or 1.6 L/alternating days.  Normally a vine would be receiving water from multiple emitters.  With newly planted vines they will only be benefitting from the water of one emitter. 

Here is an example of how long to run a drip irrigation system: If the emitter is 0.6 gallons/hr, convert to metric using the conversion factor 3.79 L/gal.

0.6 gal/hr x 3.79 L/gal = 2.3 L/hr

If we apply every other day

1.6 L ÷ 2.3 L/hr = 0.7 hrs = 42 min every other day

Traveling Gun Irrigation System:

With an overhead system water gets applied over the whole field.  Young vines have very shallow roots so there is no reason to do heavy irrigations – better to put a little on more frequently.  I recommend ¾” every 4 to 5 days.  If you can only do one irrigation, don’t bother putting on a heavier application, it will just soak below the root zone (unlike mature vines where deep roots can capture deeper soil water).

All of the above recommendations can be reduced if the ET (evapotranspiration) is less than 5 mm/day.  For current ET values see https://farmwest.com/climate/et.  Select Ontario, and the nearest weather station.  Beware! there are some errors in the graphs, click on “see daily data” to get the data in a chart format (note that across Ontario there is data missing between June 29 and July 8^th).  Another source of ET data is http://www.onpotatoes.ca/cwd.cfm.

Start irrigation early in the season.  Match irrigation demand to the canopy size and ET.  Check the efficacy of your program by using a soil moisture instrument.

All OMAFRA irrigation resources can be found here.