To reach every thirsty plant in a field or orchard, water pressure has to be just right. Tomorrow's farmers might choose to conveniently spot-check water pressure using a portable device invented by Agricultural Research Service engineers.

The pressure-tester is designed for drip-irrigation systems that use thin-walled, flexible black tubing that's either above the ground or buried. Today's drip systems irrigate an estimated 3 million acres of farmland in the United States.

Water pressure is especially critical in fields or orchards with uneven terrain, according to Dennis C. Kincaid of the ARS Northwest Irrigation and Soils Research Laboratory, Kimberly, Idaho. Kincaid and colleague Thomas J. Trout of the ARS San Joaquin Valley Agricultural Sciences Center in Parlier, Calif., invented the new tester and are seeking a patent for it.

The unit offers a practical way to determine whether an irrigation system is working properly. The tester weighs approximately one pound, is about the size of a pipe wrench, and is accurate to within the accepted 5 percent.

Kincaid and Trout have made prototypes of steel and of aluminum, and they estimate that the device could be manufactured at a reasonable cost.

The tester isn't intended to replace today's permanently installed meters and gauges, but instead is a handy option for special situations, such as for spot-checking temporary drip systems that are pulled up after harvest.

It works somewhat like a giant clothespin that's clamped around an irrigation tube and then released. A scale indicates pressure in the standard unit of measure, pounds per square inch.

Details are in the July 2003 issue of the U.S. Department of Agriculture's monthly science magazine, Agricultural Research.

ARS is the USDA's chief scientific research agency.