Application
Most herbicides are applied as water-based sprays using ground equipment. Ground equipment varies in design, but large areas can be sprayed using self-propelled sprayers equipped with long booms, of 60 to 80 feet (18 to 24 m) with flat-fan nozzles spaced about every 20 inches (510 mm). Towed, handheld, and even horse-drawn sprayers are also used.
Synthetic organic herbicides can generally be applied aerially using helicopters or airplanes, and can be applied through irrigation systems (chemigation).
A new method of herbicide application involves ridding the soil of its active weed seed bank rather than just killing the weed. Researchers at the Agricultural Research Service have found the application of herbicides to fields late in the weeds' growing season greatly reduces their seed production, and therefore fewer weeds will return the following season. Because most weeds are annual grasses, their seeds will only survive in soil for a year or two, so this method will be able to “weed out” the weed with only a few years of herbicide application.
Weed-wiping may also be used, where a wick wetted with herbicide is suspended from a boom and dragged or rolled across the tops of the taller weed plants. This allows treatment of taller grassland weeds by direct contact without affecting related but desirable plants in the grassland sward beneath.
Read more about this topic: Herbicide
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