I actually did an internship on a grape farm in the early 90's. Getting a degree in agonomy I was all hyped on modern technology and exited about tensiometers. The 20 year old me wanted to install them, but was shut down by the old Hispanic foreman during the meeting. He had been growing grapes for 30+ years. When I asked him how he decided when to water he said... simple. See these weeds growing under the grapes? (it was a type of pigweed I believe) When they start to droop it's time to water. Turns out, the grapes roots are deeper and the vines much larger than the weed, so this was in fact a free (and pretty accurate) tensiometer.

I love tech. And not to be a cynic, but I kind of doubt many serious "farmers" read this magazine. The old foreman maybe converted me to a degree of traditionalism. There doesn't need to be a tech solution for everything. Sometimes simple time tested solutions are better.

EDIT: One more point. Suppose one was able to figure out an individual plant's water needs. I don't know of any irrigation system that would let you meet it. The block, patch, field, whatever gets watered all together. Unless you send people to adjust individual emitters or something. And, if you are doing that you have undoubtedly spent far more money than you will ever make back in increased yields or water savings. This "modern farmer" magazine kind of drives me nuts and I see it posted here on HN frequently.

EDIT2: I guess I'm at my commenting limit so I'll leave the reply here. I agree with poster who says tech is necessary to feed more in the future. But this chip, in a production setting, is a non-solution looking for a problem. And there is way too much stuff like this that people think are "breakthroughs".

People have trouble comprehending scale when it comes to agriculture. A tray in a hydroponic gardens, even a roof full of hydroponic gardens... cool, but it isn't going to ever provide a significant portion of the worlds food. And it is way too expensive to set up and maintain for what it provides. Now... for specialty applications and a few off-season vegetables it's fine. But many thousands of acres and lots of water are required to produce the real bulk of our food... i.e. grains. The aquaponics systems pictured in the links below wouldn't even sufficiently feed the two guys in the picture. And... examining the moisture usage of individual plants per watering cycle... great for research or hobbyist or specialist crops, not practical day to day production agriculture. That's my point.