Sorry for the incomprehensible thread title.
I’ve been reading JamieGoode’s The Science of Wine, 2’nd edition. A terrific/informative read it is. In Chap 8, he talks a bit about irrigation and really scratches my wine geek curiosity.

  1. ABA: This is a plant growth regulator hormone. This apparently is generated in the root system of the vine when the roots sense water stress. ABA travels up the vine and sends its signal to the vine tendrils to stop their growing, that hard times are on the way, and that for the vine’s survival, it better stop its growing of tendrils/vegetation and focus now on fruit pproduction. Which is, of course, what you’re wanting for wine production.
    So, you cut off irrigation at some point to force the vine to quit growing and focus on the fruit. But if you stress the vine too much, the quality of the fruit will be compromised. So, it’s a tricky path you have to walk to achieve the best in quality of fruit. Of course, if you don’t have irrigation, you’ve lost a big tool in your bag of vnyd management tricks. This is why people like DaveGates are so important to have around.
    Question: What kind of time scale are we talking from when the root senses water stress and the ABA hormone reaches the growing tendril?? Hours, days, weeks??? What kind of time constant to these very bright grapevines operate on??

  2. RDI: This refers to “regulated deficit irrigation”. This is controlling the irrigation application to force the vine to stop its vegative growth and start focusing on fruit production. Apparently it works best but shutting off the water just after berry set, and then restoring the water after verasion to keep the berry growth healthy and not force the vine to shut down and reduce berry quality. Use of RDI has apparently been very sucessful in Australia.
    Question: How widespread is the use of RDI in Calif?? Any particularly great vnyds known to be using RDI?

  3. PRD: This refers to “partial root drying”. This requires a dual drip irrigation system where you can shut off the water on one side of the grapevine’s root system, but, alternatively, supply water to the other half of the vine’s root system. And then switch back & forth from one side to the other in 1-2 week intervals. So one half of the root system signals the plant to stop growth and focus on fruit production, but the other half of the root system has the resources to keep the vine alive & healthy. Apparently, use of PRD has a big benefit in reduction of water usage, by almost half…something that might be of interest in Calif I would think. This is an important issue in Australia I gather.
    Question: Is there anybody practicing PRD in Calif?? I would think there is a good business opportunity here for vnyd management companies in Calif to convert conventional drip irrigated vnyds to PRD.

Of course, this is all irrelevant in France…where they’ve chosen to forbid irrigation and throw themselves at the mercy of ole Mother Nature. Which, of course, explains why their wines are so crappy.

Anyway…just a few ?? that Jamie’s book has provoked. Doubt I’ll get any answers, but thought I’d try.

No info from me. :slight_smile: But then, it’s irrelevant for France anyway! :slight_smile: