The participating agencies include: the Coachella Valley Resource
Conservation District and the Imperial Irrigation Districtboth
of California; Yuma Agricultural Center, Yuma, Arizona; and the U.S.
Bureau of Indian Affairs, along with the Natural Resources Conservation
Service office in Parker, Arizona.
"Many growers in these areas have only had very basic soil tests
to diagnose complicated salinity issues. Others draw conclusions about
the state of their soils simply through visual surveys," says University
of California statistician Scott M. Lesch. Located at the Riverside
laboratory, Lesch assists ARS as the LCRSAN technical program coordinator.
With USBR funding, each area received salinity-assessment field equipment
that was developed at the salinity laboratory. The mobile rig, better
known as the "Salt Sniffer," uses a new electromagnetic inductance
meter that seeks out salt in the soil. The meter relays conductivity
survey data to a real-time GPS receiver. The survey and location data
are stored in a GPS data logger, which can then be downloaded and used
to produce maps of a field's soil patterns.
Lesch and colleagues provided training on the remote-sensing soil-assessment
equipment and continue to offer day-to-day advice on the various aspects
of soil surveying. Lesch also trains field specialists on using the
software, which interprets data gathered in the field.
Together, the equipment and software can inform growers about a range
of soil conditions, including salinity levels, salt-loading characteristics,
and soil texture. A useful product of the software is a sampling plan
that can direct a farmer to parts of a field that are showing some sort
of variability. Soil samples can then be taken to determine precisely
what's causing the irregularity.
The software package is called "ESAP." The current version,
2.30, can be downloaded free of charge from the Salinity Laboratory's
web site at www.ussl.ars.usda.gov.
(Click on "Models.") Lesch says there are now about 200 registered
users of the software across North America and Australia.
An ideal use of the LCRSAN program's equipment and software, says ARS
soil scientist Dennis L. Corwin, is to assess the practice of using
recycled drainage waters to irrigate fields. Making use of these waters,
which are generally considered low quality and hard to dispose of, could
greatly conserve fresh water sources, reduce drainage water disposal
problems, and enhance on-farm efficiency.
But many farmers may be leery of using recycled waters for fear of
damaging their crops. "With the equipment, you can monitor small
changes in the soil over time," Corwin says. "You can see
whether applying recycled waters is a sustainable practice and find
out to what extent the water can be safely and effectively used."
Another application of the field equipment and associated software
is a newer practice known as precision leaching. "If a farmer believes
his land is suffering from saline conditions, he'll often reclaim the
land by applying additional waters, to leach out the excess salt,"
says Lesch. "But, in many cases, the farmer may unnecessarily leach
an entire field to remedy just one area that's experiencing high salinity.
The ARS equipment can be used to find and treat just the problem spots,
which would conserve water."
The Next Step
Most members of the LCRSAN network are up and runningcapable
of producing informative soil-salinity maps and profiles. The Imperial
Valley, a productive agricultural center in southern California, recently
completed its 100th salinity survey.
"While there is a growing awareness of the problem of salinity
in the region, we still don't know how extensive it really is. There's
no current inventory of saline conditions throughout the country,"
The concept of developing mobilized equipment that can assess salinity
across vast areas started with James D. Rhoades, former director of
the Riverside laboratory. His successors hope that these technologies
can be used to their full potential throughout the United States and
worldwide. They'd also like to someday pool the incoming salinity data
from several local districts to assess salinity on a broader scale.
In the meantime, the salinity lab is continuing to develop resources
to ease the task of identifying and improving saline soils.
"We're developing decision-support software that would supplement
existing software," says current lab director Donald L. Suarez.
"It would make specific recommendations to farmers and growers
trying to make management decisions based on data from soil surveys."By
Erin K. Peabody,
Agricultural Research Service Information Staff.
This research is part of Water Quality and Management (#201) and
Soil Resource Management (#202), two ARS National Programs described
on the World Wide Web at www.nps.ars.usda.gov.
To reach scientists mentioned in this article, contact Erin
Peabody, USDA-ARS Information
Staff, 5601 Sunnyside Ave., Beltsville, MD 20705-2350; phone (301)
504-1624, fax (301) 504-1641.
"In Search of Salt: Managing Salinity in the Lower Colorado
River Region" was published in the September
2004 issue of Agricultural Research magazine.