One of the first things I learned from my father–in–law, a wine grape grower of 40 years, was what to look for when it was time to start irrigating. There was a lot of technology a decade ago – neutron probes and tensiometers – at the same time there was nothing like looking at the vine to know when it was time to turn on the drip system.
First, we run through the data. What did the instruments that measured the amount of water in the soil indicate? Walker Vineyard had been relying these technologies for years. They are very accurate and, in the case of the neutron probes, they were part of a system used by the local irrigation district that partnered with farms to provide irrigation recommendations.
In short, we use technology for to measure the moisture in the soil and indicate how much water to apply.
We use physiological indicators from the vine to tell us when to start to irrigate. The objective is to hold off irrigating until the vine stops growing is showing the stress of water deficit. At the tips of the canes the new leaves will turn brown and die effectively stopping the growth.
At the base of the vine, leaves turn red and then brown and start fall off. This is another indictor that it is time.
Really the vines are starting to die but just a little!
Using technology to tell us how much water to apply and only starting the irrigation when the vine growth has stopped, ensures that bunches that are now forming nicely will be supported by a well–balanced vine.