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Apply Herbicide As You Combine
Researchers at Oklahoma State University recently added a sprayer to a combine so that herbicides could be applied on the weed canopy of just-cut grain while the straw and chaff was still in the machine.
Used primarily in minimum and no till wheat, and double crop situations, the combination of harvesting and spraying eliminates a separate trip across the field to apply herbicides. Plus, it helps the chemicals be more effective since they don't have to penetrate through a heavy layer of straw. And, with the spray booms under the combine, there's less wind drift.
H.W. Downs, ag engineer at OSU, explains that the spray system was mounted directly on the header while the center section was mounted just in front of the rear tires since there wasn't room enough under the feeder housing for it. Downs cautions that if you attempt to add a sprayer to your combine that you keep the sprayer away from the combine fan.
He explains that the spray system he and his co-workers developed was experimental and would vary depending on the type of combine being used. In the OSU experiment, the booms were mounted so they rode about 18 in. high. Flood jet type nozzles were spaced 20 in. apart.
Researchers used a 35 gpm certrifugal pump belt driven off the engine's output shaft but that a hydraulic pump could also be used. The 200 gal. spray tank was mounted behind the combine engine.
Downs says that one tricky part of the set up is keeping application rates constant as ground speed changes. He says that automatic control systems that vary the amount of chemical injected into the water as ground speed varies for a constant application rate may be the answer to the problems.

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1984 - Volume #8, Issue #1