Scientists advise farmers on how to make sure water flows to right place
By TIM HEARDEN
CORNING, Calif. -- As water demand increases in California and shortages become more severe, advances in irrigation efficiency will become all the more crucial for growers.
Years of research have given University of California scientists an idea of exactly how much water each tree needs and when, and microirrigation technology allows them to apply the water almost directly to the roots.
Now UC Cooperative Extension advisors are urging orchardists to make use of their gains. They say such attention to detail will greatly lessen water losses from runoff or leaching to aquifers.
Irrigation efficiency "means the water goes to the crop, or goes for frost protection," irrigation specialist Larry Schwankl told about 70 plum and nut farmers at a workshop here Dec. 5.
Growers should care about efficiency because of rising costs for pumping groundwater or purchasing surface water and because of limited availability of water, said Schwankl, who works at the UC's Kearney Agricultural Research and Extension Center near Fresno.
"Inefficient water use is tied to nitrate leaching," Schwankl said. "Putting on the right amount of water at the right time involves irrigation scheduling and good knowledge of the system."
Extension advisors have set up several websites and issued publications that tell growers the rate of evapotranspiration -- the rate of evaporation from the ground and transpiration from tree leaves -- depending on such factors as the type of soil and time of year.
Growers can put this information along with the crop load of a given tree into an equation to come up with how much water to apply. To make sure trees are getting the right amount of water, water advisors including Allan Fulton in Red Bluff, Calif., encourage growers to invest in such testing technologies as pressure bombs, which are sort of like blood pressure tests for tree leaves.
Fulton also urges producers to seek consultations with experts for help with their irrigation management.
"It's pretty clear there's plenty of room for teamwork in all these issues that we're facing," Fulton said.
One of those experts is Kevin Greer, who operates a mobile irrigation lab for the Tehama County Resource Conservation District. The lab has done 330 orchard analyses in the last four years, including over 100 in the last year, he said.
Farmers should understand the importance of uniformity in their water deliveries so none is wasted, he said. No orchard floor is perfectly flat, so growers need to compensate for small dips and peaks by balancing their water pressure, he said.
They can also minimize the lack of uniformity by using the same sprinkler types and nozzles throughout the system and maintaining the lines, which can get clogged or develop leaks, he said.
Schwankl encourages growers to use flow meters to electronically track how much water they're applying. Soil-moisture monitors and plant-based monitors can show if the water is getting to the right places.
"We're all trying to nail down this efficiency and be better irrigators," he said.
University of California Cooperative Extension Water/Irrigation Program: http://cetehama.ucdavis.edu/Water___Irrigation_Program/
California Irrigation Management Information System: http://wwwcimis.water.ca.gov/cimis/welcome.jsp
UC Drought Management: http://ucanr.edu/sites/Drought/
Tehama County RCD Mobile Irrigation Lab: http://www.tehamacountyrcd.org/services/lab2.html