So we have been growing the vines at Arrow Lakes Vineyard with the very least amount of water we can. We tried zero irrigation and wanted to rely on rain fall alone and while that seemed like not a bad idea given our very short growing season, we could not make it through the super hot summers without severe vine stress especially when some days are seeing the temperatures getting above 35c.
The alternative was to have very low crop loads to the level that would not be economical. So we widened the space between rows a bit from 6-7 feet to 8 feet and installed drip irrigation that is active only during the hottest periods when the vines could get damaged by water stress. The wider rows gives the vines a bit more area from which to draw water from the soil and we turn the minimal irrigation on for a short period generally between July 1st and August 31st - so just to get the vines through the hot periods.
The most important factor we have found to limiting the irrigation we need to apply is through eliminating the weeds and growth between rows. The fact is the monashee area actually gets some decent rain fall throughout the summer months - significantly more than the Okanagan gets. However, the rain that does fall has little chance of being utilized by the vines if it is intercepted by weeds or grass between the rows.
So to eliminate weeds we have relied mostly on solarization and cultivation between the rows. We do solarization between the rows by applying clear plastic (same type used for vapour barrier on houses) between the rows. The roll is 12' x 175' so we cut it to 6 foot wide and we can do two rows at a time. You lay the palstic down and shovel dirt along the edges on both sides and a bit in the middle so it doesnt blow away. Then the sun bakes the weeds underneath and after about 3 weeks there are no more weeds. Then we move the plastic to a new row. Its a bit labour intensive but the effects are so good that the rows will remain weed free for years.
To compliment this we do regular cultivation in the spring, early June and early July then thats it, no more required. After that point its too hot and dry for weeds to really get going. Some weed eater work under the vines keeps the bigger weeds and grass in check also.
So with the weeds in check the rain that does fall doesn't require much in the way of suppliment from the irrigation.
