Picture a quarter-mile wide spray rig. Now picture it running Saturday at midnight.

Cotton farmers with center-pivot irrigation systems will have access to that type of chemical applicator later this year or early in 2000 when a new system from Valmont Irrigation hits the country. Field tests are now in progress.

Called Accu-Pulse, the system can be retrofitted to work with Valley, Zimmatic and practically any other brand of pivot now stretching across West Texas, New Mexico, Arizona and other cotton states, says Greg Bartlett, Valmont senior product manager in Valley, NE.

In the Accu-Pulse system, an independently operated spray boom is attached to the pivot. The boom and its 1 1/2" poly-pipe are connected to a 1,000- or 1,500-gallon injection tank separate from the irrigation water supply.

A computer-driven hydraulic system injects chemical and water into the pipe. Chemical is applied in an intermittent pulsing manner via nozzles. Large droplets help protect against drift.

The system can apply chemicals using only 20-30 gallons of water per acre. That compares to a chemigation system that uses 3,500 gallons or more.

"It should really benefit growers in our area," says Heath Allen, a Valmont dealer in Seminole, a West Texas region where irrigated cotton is the major cash crop. "We've discussed it with our growers and they look forward to seeing it in operation on cotton."

With disease, weed and other problems, cotton sees large chemical inputs that can swell costs of production. With the new system, growers are not limited to chemicals labeled specifically for chemigation. They may use chemicals labeled for a ground rig as well.

"The pulse-type application helps provide good uniformity to cover the entire canopy and assure good coverage of targeted weeds, insects or diseases," says Rich Panowicz, Valmont senior application engineer.

"This can be important for cotton growers, who often face multiple applications of six or more treatments a season. Chemicals can be applied with more precision than an aerial applicator."

Flexibility is a key factor, too.

"Chemical can be applied whenever a grower wishes," says Panowicz. "Since chemical is applied using the pivot's field tracks, there is less compaction."

Bartlett says about 50 of the units are being field-tested in potato-growing areas of Idaho and Minnesota. So far, he adds, there is no definite price tag on the system. But he expects growers to be able to buy it with a four- or five-year payoff program that fits their management plans.

For further information on the system and how it will work on a particular center-pivot brand, contact Valmont at 800-825-6668.