Nov 95 Level of Govt: State. Function: Transportation Management. Problem/situation: Weeds that grow along highways are costing California $25 million annually. Solution: Weed-seeking technology helps destroy weeds more efficiently, saving money and chemicals. Jurisdiction: California. Vendors: Patchen California Inc. Contact: Cal Schiefferly, Caltrans, 916-227-9604, fax 916-227-0977; Larry Shields, Caltrans, 916-654-4329, fax 916-653-3291
SACRAMENTO, Calif. - Among the human endeavors that call for high technology, killing weeds seems to rank in the lower strata. Yet weeds are exactly what the California Department of Transportation (CalTrans) is targeting with its latest application of technology. Department officials have leased an innovative sprayer that uses computer technology and advanced optics to determine whether a weed is present. If so, the sprayer triggers the appropriate nozzle and the weed is sprayed. If not, the machine passes over the ground without firing. The result is that only weeds are sprayed, not bare ground. The savings in chemical usage can be tremendous. That's important not only from a budgetary standpoint, but also in helping the department meet its goal of cutting chemical use by 50 percent by the year 2000 and by 80 percent by 2012, explained Larry Shields, landscape program administrator for Caltrans. "We believe we can save 40 percent of our spot treatment chemical use," he said.
Tracking Chemical Use The sprayer also ties into other aspects of the coming computer revolution in agriculture. Because the sprayer utilizes computer technology, on-board memory can be added. That means it can record chemical use data, which can be downloaded into an office computer. If Caltrans wants, it could also note the exact location of the chemical application by equipping the truck with field-mapping software and a Global Positioning System (GPS) monitor. The department leased the sprayer in June. In the first trials, the sprayer has worked as advertised. But there have been logistical problems. The sprayer is used to control weeds along state highways, and the many physical obstacles present - guardrails, signposts, etc. - mean that operators must periodically adjust the sprayer's boom. In addition, the boom's eight-foot-width makes it too long for the three-foot and five-foot strips found along some highways. Those are correctable problems, said Dale Wallander, sales representative for Los Gatos, Calif.-based Patchen California Inc., the company that manufactures the sprayer. The width is an easy fix, he said. The sprayer has individual sensors and nozzles, and the numbers of each can be chosen at the time of ordering. The physical obstacles along roadways are a bigger hurdle, but can be overcome by adding hydraulics to raise and lower the boom, adding a hinge that would allow the boom to snap backward until it clears the obstacle, or some other engineering feature, Wallander said. "There's always a way to sit down and redesign the spray bar," he explained. Six months will be used to experiment with the sprayer, and to get feedback from the operators who run the equipment. "This is still in the early stages," explained Cal Schiefferly, associate equipment engineer with Caltrans. "We need to see how the equipment actually works in the field. I don't have any concerns about its ability to spray weeds, but we need to hear back from the operators before we'll know how it's going to work and what kind of changes we'll need to make." The sprayer - called the WeedSeeker - emits thousands of bursts of light each second. Within that spectrum are a couple of wavelengths that announce the presence of chlorophyll. A sensor notes that, and triggers the appropriate nozzle. The sprayer was introduced four years ago into the agricultural market. Caltrans will use it much as California farmers do - as an alternative to spot spraying by hand. Caltrans oversees 15,000 miles of roadsides and has an annual weed control budget of $25 million. The standard program is to spray a pre-emergent herbicide on the shoulders of the road, then