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True Grit in Battle Against Weeds

battle-against-weedsU.S. Department of Agriculture agronomist Frank Forcella has devised a tractor-mounted system that uses compressed air to shred small annual weeds like common lambsquarters with high-speed particles of grit made from dried corn cobs. Ongoing field trials may confirm the system’s potential to help organic growers tackle infestations of weeds that have sprouted around the bases of corn, soybean and other row crops.

Dubbed “Propelled Abrasive Grit Management” (PAGMan), the weed control system Forcella is testing disperses 0.5-millimeter-sized grit particles in a cone-shaped pattern at the rate of about 300 pounds per acre using 100 pounds per square inch of compressed air.

This summer marked a second round of field trials of PAGMan on multiple rows of silage corn grown on 10-acre plots of certified organic land in Minnesota. Field trial results from 2013 showed season-long weed control levels of 80 to 90 percent in corn using two treatments of the abrasive grit-one at the first leaf stage, and the second at the three- or five-leaf stage of corn growth. Corn yields also compared favorably to those in hand-weeded plots used for comparison.

The crop plants escape harm because they are taller than the weeds during treatment and their apical stems (growing points) are protected beneath the soil by thick plant parts. Results from small-plot studies have been published in Weed Technology and other journals.

This article appears in the October 2014 issue of Acres U.S.A.

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