Development and Demonstration of a New Method of Physical Weed Control
This project commenced in December 2010. Consequently, 2011 was the first full year in which portions of the proposed research and engineering could be accomplished. Highlights during this time include the following in chronological order: (i) SDSU graduate student in Agricultural and BioSystems Engineering was recruited; (ii) farmer-collaborator meeting held in April in which four organic growers, three engineers, and two weed scientists shared and refined ideas about the new concept and proposed technology; (iii) field-testing of a prototype grit applicator was performed successfully on soybean; (iv) manuscript describing successful field-tests of prototype grit applicator on corn accepted for publication in the peer-reviewed journal, Weed Technology; and (v) fabrication began of four-row demonstration model of grit applicator, in anticipation of the 2012 field season. Additionally, the concept and preliminary experimental results were extended by invitation to five audiences during 2011: three organic grower meetings (combined audience of about 175), one professional meeting (audience = 200), and one university classroom (audience = 20). Lastly, this new concept in weed management, including data, slides, and a brief video are being incorporated into the Organic Agriculture course taught by Professor Sarah Ward at Colorado State University.
Our first objective during the start-up year of this project was to hire a post-doctoral research associate in agricultural engineering. However, because of the current economic climate, agricultural engineers are in very short supply; that is, they are hired by industry immediately upon graduation. In lieu of a post-doc, we enlisted the assistance of Dr Dan Humburg (Professor of Agricultural Engineering at SDSU) and recruited his graduate student, Mr Corey Lanoue. Dr Humburg and Mr Lanoue proved to be invaluable assets to the project. They spent much of 2011 designing the intricate and inter-connected parts of a hypothetical four-row grit applicator. In the latter two months of 2011 they commenced fabricating these parts and assembling them (Fig. 1). The grit applicator is expected to be ready for field-testing by May 2012.
The grit applicator is comprised of several parts, including a PTO-driven air compressor, a toolbar that doubles as a manifold for even distribution of compressed air, two grit tanks that are pressurized (slightly) at 5 psi, four grit meters immediately below the grit tanks, and eight nozzles arranged in pairs. The meters and nozzles are being fabricated in-house. The meters feed grit at adjustable rates into the nozzles. The nozzles are designed specially to reduce grit-induced wear. That is, grit is entrained in the compressed air stream only at the replaceable nozzle tip, which should greatly improve lifespan of the orifice where necessary air-speeds are generated. Although still under construction, this implement is indeed a novel device in agricultural circles.
Another objective for 2011 was to test the feasibility of using abrasive grit in soybean. Previous work in corn using a prototype single-row grit applicator was highly successful, and these studies should appear in published form in the first issue of Weed Technology in 2012. However, corn and soybean seedlings differ greatly, and we feared abrasion by grit may be detrimental to soybean. A field experiment at the Swan Lake Research Farm (MN) was performed in 2011 in which grit was applied to soybean seedlings at the VE, VC, VU, V1, VE+VC, VC+VU, VU+V1, VE+VC+VU, and VC+VU+V1 stages of growth. Soybean yield was lowered only in the VE+VC+VU treatment. All other treatments yielded the same as untreated control plots. These results are highly encouraging and indicate that abrasive grit can be used successfully in row crops other than corn. Because of the tentative nature of this experiment, we chose not to showcase it to growers at our annual August Field Day. Analogous experiments will be showcased in 2012.
The following publications are associated with this project:
Forcella, F. 2011. The needle in the hay stack: Keeping it lost [abstract]. Weed Science Society of America. Available: wssaabstracts.com/public/4/abstract-263.html.
Forcella, F., S. Clay, D. Humburg, and C. Lanoue. 2012. Field application of abrasive grit for postemergence weed control in corn and soybean [abstract]. Weed Science Society of America. Available: wssaabstracts.com/public/5/abstract-279.html.
Forcella, F. 2012. Air-propelled abrasive grit for postemergence weed control in field corn. Weed Technology 26: in press.
Impacts and Contributions/Outcomes
- The research on development of an abrasive grit applicator was described, by invitation, at the following five meetings during 2011:
Northern Plains Sustainable Agriculture Association, “Blasted weeds!” Fargo, ND, February 2011. (Grower audience of about 100)
Weed Science Society of America. Invited by herbicide resistance symposium organizers to present the paper “The needle in the haystack: Keeping it lost.” Portland, OR. February 2011. (professional audience of about 200)
Southern Minnesota Organic Crops Day, University of Minnesota Extension, “Blasted Weeds!” Owatonna, MN. March 2011. (Grower audience of about 25)
University of Minnesota Gopher Crops and Soils Club, “Blasted Weeds!” St Paul, MN, March 2011. (Student audience of about 20)
Sioux Falls Organic Agriculture Conference, SDSU Extension, “Blasting weeds,” Sioux Falls, SD, December 2011. (Grower audience of about 50)
South Dakota State University
Brookings, SD 57007
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