A team of plant and soil scientists from California State University, Fresno and the University of California, Davis is working to provide new water-use estimates for crops grown under saline conditions on the West Side of the San Joaquin Valley.
Leading the work at Fresno State is Diganta Adhikari, an irrigation scientist for the university’s Center for Irrigation Technology. Among key partners in the work is biometeorology specialist Richard Snyder of the Department of Land, Air and Water Resources at the UC Davis.
The project goal is to develop a portable weather station that West Side water districts or large-scale growers could use to directly measure crop evapotranspiration (ET). This would improve irrigation with water containing high levels of salt, boron and selenium, a common factor in the area.
“Crop evapotranspiration data is already available for most crops,” Adhikari said. “But when salinity comes into the picture, everything changes. ET can be lower if the soil or water salinity is high enough to substantially reduce growth. We basically do not have those numbers.”
To develop accurate ET information for a crop, scientists use data gathered from an agrometeorology station in a nearby grass field that measures air temperature, humidity, wind speed and several other environmental conditions.
The meteorological data are used to estimate reference evapotranspiration, which is roughly equal to that of well-watered pasture grass. The California Irrigation Management Information System provides such reference information for most agricultural areas.
Considerable research to determine crop coefficient values has been conducted over the years. However, a key need for the West Side is salinity coefficients to account for high-salinity soils or crops irrigated with water high in salts, Adhikari said.
“The water districts started calling us, saying, ‘We know how much water is needed under normal conditions, but we want to know the needs under saline conditions,’” he said.
The ultimate objective of the project is to provide West Side growers with evapotranspiration estimates for crops grown under saline conditions on the West Side, Adhikari said, which accounts for more than 400,000 acres (about 625 square miles).
Calibration and data collection work will continue through this year, with conclusions on the work expected to be released next year, Adhikari said.
For more information, contact him at diganta@csufresno.edu.
(Copy by Steve Olson, publications editor of the California Agricultural Technology Institute at Fresno State.)
