ARS | Publication request: Post-emergence weed control through abrasion with an approved organic fertilizer

Submitted to: Renewable Agriculture and Food Systems
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 19, 2010
Publication Date: January 1, 2011
Repository URL: http://hdl.handle.net/10113/49261
Citation: Forcella, F., James, T., Rahman, A. 2011. Post-emergence weed control through abrasion with an approved organic fertilizer. Renewable Agriculture and Food System. 26(1):31-37.

Interpretive Summary: An entirely new form of post-emergence weed control was tested. Corn gluten meal (CGM) is an approved organic fertilizer (10% nitrogen) and preemergence herbicide that can be manufactured in the form of grit. This grit was examined for its ability to abrade seedlings of the weed, yellow foxtail, by expelling it from a sand blaster at air pressures of 40 to 120 psi at distances of 1 to 2 ft from the plants. Established foxtail seedlings were controlled better when grit was applied at 80 and 120 psi than at 40 psi, as well as when the applicator’s nozzle was 1 ft from the plants compared to 2 ft. As little as 1 or 2 seconds of exposure to grit often killed plants. Additionally, CGM, which is considered a soft grit, was as effective for controlling seedlings as fine quartz sand, a hard grit. CGM also has been reported to have pre-emergence herbicidal activity on some weed species, but it did not exert this effect on foxtail. Although foxtail regrowth can occur after abrasion by grit, the initial grit-induced stunting is sufficient to allow competing crop plants, like corn, to escape competition and suppress the weed. Consequently, CGM may be an effective form of soft grit for post-emergence abrasion of seedlings of summer annual grass weeds in organic row crops while simultaneously supplying the crop with nitrogen fertilizer. This new ARS-developed technique potentially allows simultaneous nitrogen fertilization and post-emergence weed control in organic crops. Consequently, these results may be of interest to manufacturers of agricultural machinery as well as organic growers of crops that grow in widely spaced rows, such as corn, sweet corn, grapes, blueberries and brambles.

Technical Abstract: Corn gluten meal (CGM) is an approved organic fertilizer and preemergence herbicide that can be manufactured in the form of grit. This grit was tested for its ability to abrade seedlings of the summer annual weedy grass, Setaria pumila, when plants were in the 1- to 5-leaf stages of growth. It was propelled at air pressures of 250 to 750 kPa at distances of 30 to 60 cm from the plants. Established seedlings of S. pumila were controlled more effectively when grit was applied at 500 and 750 kPa than at 250 kPa, as well as when the applicator’s nozzle was 30 cm from the plants compared to the 60-cm distance. Seedling growth and dry weights were greatly reduced by exposures to grit at 60 cm and 500 kPa for only 2 seconds or less. At 750 kPa and 30-cm distance, seedlings were nearly completely destroyed. CGM, a soft grit, was as effective for abrading seedlings as fine quartz sand, a hard grit. CGM had little preemergence herbicidal effect on S. pumila. Although regrowth can occur in S. pumila after abrasion by grit, the initial grit-induced stunting is sufficient to allow competing crop plants, like maize, to escape competition and suppress the weed. Consequently, CGM may be an effective form of soft grit for postemergence abrasion of seedlings of summer annual grass weeds in organic row crops whilst simultaneously supplying the crop with fertilizer.