Reading plant stress can be a difficult endeavor, especially for nuts or wine grapes, where deficit irrigation is desirable near harvest, writes Christina Herrick at Growing Produce. Currently, pressure chambers are the most common way to measure plant stress.
“It’s a big heavy instrument. You cut a leaf off and you stick it in the chamber, and you have to increase the pressure,” Alan Lakso, Emeritus Fruit Crop Physiologist with Cornell University, says. “It’s a slow, manual process, and then you get a reading of what the stress is that one moment that you took the leaf off.”