Salt-Tolerant Forages for Irrigated Areas

Alfalfa may help solve a problem that’s been plaguing farmers and land managers for years in California, according to scientists with the Agricultural Research Service and their collaborators.

The state’s San Joaquin Valley is one of the world’s most productive agricultural areas, sometimes referred to as “the nation’s salad bowl.” Unfortunately, the irrigation systems that bring water to the valley’s fruits and vegetables also transport salts that thwart plant growth. Salt makes it harder for plants to absorb the water they need.

In view of the restrictions on discharge of drainage waters and in an effort to use water more efficiently, members of the federal/state interagency San Joaquin Valley Drainage Implementation Program recommended that farmers plant salt-tolerant vegetation and use saline drainage water to irrigate it.

A few years ago, ARS scientists at the George E. Brown, Jr., Salinity Laboratory in Riverside, Calif., tested eucalyptus to see if it would be effective at extracting excess saline drainage water. They found that although eucalyptus trees can survive on a diet of salty water, they suffer from salt stress. The trees don’t die, but they don’t grow either, so they don’t use up very much of the saline water.

Since then, the scientists have turned their attention from eucalyptus to salt-tolerant forages--plants that could possibly reduce drainage water volumes while producing a feed source for sheep and dairy cattle. Along with collaborators at the University of California-Davis and California State University-Fresno, the salinity lab scientists conducted a controlled study to evaluate promising forage crops.

The researchers used an elaborate sand-tank system at the salinity lab and tested a variety of forage species. They ranked these species by factors such as production potential and forage quality. Overall, alfalfa cultivars performed best under the controlled conditions of the experiment. Although the results are promising, the researchers will conduct field tests and ruminant nutritional studies before they make any recommendations.

ARS is the chief scientific research agency of the U.S. Department of Agriculture.