Water study

A group of Eddy co-variance systems is calibrated in a field near Yuma for an ongoing study of water use and soil salinity being coordinated by the Yuma Center for Excellence in Desert Agriculture.

A long-range study coordinated by the Yuma Center for Excellence in Desert Agriculture analyzing water usage and salinity in desert crops recently won $135,000 in new grant funding from the U.S. Department of Agriculture.

Paul Brierley, YCEDA's executive director, said the study has been ongoing for three years, and the new money will help it meet its goal of five years' worth of data on water usage by different crops in the desert.

"The numbers being used now to estimate water usage are from the 1950s, and the crops are a little different today, they're a lot higher yielding, so we're getting good updated data and that can be useful for irrigation management," he said.

These numbers will be especially useful for automated irrigation systems, which can release water based on daily weather and other local conditions.

The study, titled "Quantitative Assessments of Water and Salt Balance for Cropping Systems in Lower Colorado River Irrigation Districts," is led by Dr. Charles Sanchez of the University of Arizona and Dr. Andrew French of the Maricopa research center.

A host of other agencies and industry groups are participating as well, contributing up to half the $2 million that's been invested in the research so far through in-kind donations of land and expertise.

The infusion of federal money has come from two USDA programs:

• $87,000 from the Specialty Crop Block Grant program, for analysis of Brassica crops, which include broccoli, cauliflower, cabbage, Brussels sprouts and kale.

• $45,000 from the USDA Arid-Land Research Center in Maricopa for operation of field monitors used to track crop water usage and soil salinity. These include the solar-powered Eddy covariance systems, which measure evapotranspiration, and drones, which are used to check the data on satellite images provided by NASA's Jet Propulsion Laboratory.

The study employs monitors like the Eddy systems, in-air drones and satellites from NASA's Jet Propulsion System to zero in on how much water the crops use, and also how much water is needed to leech out enough salt from the soil for the crops to survive.

Both of these vary from plant to plant, and some can even push salt crystals further underground, making them a good choice to rotate with others that are more salt-sensitive, including lettuce.

The scope of the project has expanded as producers of different commodities have come on board, Brierley said: "Each of them has their own interested parties, and they've helped to fund that specific crop within the context of the project."

The research began by focusing on leaf, romaine and iceberg lettuce, durum wheat, sudangrass and spinach, along with a fallow field. The more recent entries are cantaloupe, watermelon, cotton, cauliflower, broccoli, spring mix and barley.

It started out as a collaborative project, and has multiplied as more partners come on board, helping to extend the length from the original plan of three years to five.

Brierley said the preliminary results of the study have found significant differences in water use between the crops as measured 70 years ago versus today, up to 20 percent.

Unfortunately that's in the plus column, but Brierley said it's not necessarily bad news: "If you're using 20 percent more water but getting 50 percent more yield, then that's a pretty good investment."

Part of the next stage will be making the updated numbers available to other researchers as well as producers, something a cybercommunications team at UA is currently working on, he said.


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