Website helps California nut, grape growers improve irrigation

04/28/2014 11:22:00 AM
Vicky Boyd

The University of California, Davis, has launched a new website to help almond, walnut, prune and grape growers in the state optimize irrigation.

The site, developed by the university's Fruit and Nut Research and Information Center, focuses specifically on calculating stem water potential—a measure of how well irrigated or water-stressed a plant is, according to a news release.

Stem water potential is based on readings from pressure bombs, also known as pressure chambers.

Users remove selected leaves from plants during the middle of the day and insert the stem into the pressure chamber.

Ken ShackelCourtesy University of California, DavisKen Shackel (right) checks out the stem water potential of a leaf in a pressure bomb, also known as a pressure chamber.The machine then measures how much pressure it takes before a drop of water appears at the end of the stem. The number can be easily translated into a water-stress level.

Because different plants handle water stress differently, baseline values vary.

“Measuring water stress, or what we call stem water potential, at midday is like taking a blood pressure reading during exercise," Ken Shackel, plant physiologist, said in the release. "When the weather is hot and dry, it's normal for the plant to be working harder to pull water, even if the soil is wet. The website calculates stem water potential expected for a plant in wet soil, under the weather conditions for that day. We call that the ‘baseline' value.

“If your tree's stem water potential is close to the baseline value, adding water to the soil won't change how your tree is feeling.”

What the website does is provide baseline water-stress readings for specific crops under similar conditions.

Users enter the date, the time and closest weather station to obtain the reading.

They can then compare their readings to fully wet-soil conditions.

The university plans to eventually expand the website to include baseline values for other crops.



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