At this time of year (September) you should stop watering your grapes to encourage them to acclimate properly for winter. While you can’t control the rains you can certainly turn off the watering system to your grape vines for the next month. If your vines are less than one year old watering should have been stopped by mid-August or even earlier. Young vines are much more vigorous than older vines and need more encouragement to acclimate properly for winter. Withholding water provides that encouragement. You should also avoid the application of any nitrogen fertilizer at this time of year as this can stimulate growth resulting in winter damage.
After the first fall frost (but no sooner than October 15)
Turn your irrigation system back on and thoroughly water the vineyard. The roots of your grapes may be three, four, or five feet deep thus it may take hours to apply enough water to fill the soil profile to the lower depth of the roots.
|Drip tube running along the lower wire of the trellis.|
If you are using a sprinkler system apply a foot of water. Apply it slowly to allow it to be absorbed by the soil and not run off. Many sprinkler systems apply an inch of water or more per hour so you will need to turn off the sprinklers. This is much too fast for the water to be absorbed by the soil. When the water starts to run off. Wait an hour and turn the system back on. You may have to do this a number of times to apply the amount of water needed by the plants to carry them through until spring.
Ditch vs. Domestic Water
If you use irrigation water the ditch may be shut off before mid-October requiring you to irrigate earlier than the first frost. If you have access to treated water, delay this last application of water of the season until after October 15. Don’t make the mistake of using well water or water from a drain ditch to irrigate your vines unless you have tested it for salts and the sodium adsorption ratio (SAR) and been approved for irrigation use. Once you have watered for the last time of the season be sure to winterize the system to avoid winter damage and costly repairs next spring. If the winter is open and dry watering your vineyard in mid-winter is recommended.
The first fall frost in Mesa, Delta, Montrose, and Ouray counties varies with the community as can be seen on the web page at http://www.coopext.colostate.edu//TRA/PLANTS/climate.shtml .
Information on SAR is at http://www.coopext.colostate.edu/TRA/PLANTS/sar.html.
See the fact sheet on winterizing your irrigation system at http://www.ext.colostate.edu/pubs/crops/04719.html.
Information on winter watering is at http://www.ext.colostate.edu/pubs/garden/07211.pdf.