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United States Department of Agriculture

Agricultural Research Service

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Research Project: Development and Demonstration of a New Method of Physical Weed Control

Location: Soil Management Research

2011 Annual Report


1a.Objectives (from AD-416)
Engineer, field-test, and demonstrate a novel method of postemergence weed control that employs abrasive grit propelled by compressed air. Development of field-scale equipment and intensive field validation are required for this promising new technique, which is expected to meet certified organic standards.


1b.Approach (from AD-416)
Engineering approaches involve: (i) harnessing a tractor's energy to compress air (~500 kPa) sufficiently for (ii) propelling crop-derived grit in a directed fashion through nozzles at speeds that abrade small weed seedlings selectively within crop rows, (iii) adapting nozzles for optimum patterns of grit application, and (iv) attaching multiple pairs of nozzles onto a tractor-mounted toolbar for simultaneous multiple-row weed control. Field research entails testing: (i) the timing and frequency of application passes, (ii) air pressure or grit air speed requirements, and (iii) grit size and hardness, e.g., walnut (hard) vs. corn cob (soft), to affect season-long control of weeds without crop injury in common annual and high-value perennial row crops. Demonstrations include displays of prototype equipment in action and their selective effects on weeds and crops at field days in Minnesota and South Dakota. Outcomes anticipated comprise: (i) a novel and tangible implement for non-chemical weed control; (ii) two peer-reviewed articles, one in an engineering journal and another in an agronomic journal; (iii) an extension bulletin describing the new system; and (iv) possible patents for the resulting implements. The expected audiences for the project are organic growers and equipment manufacturers. Both audiences will be exposed to an entirely new form of physical weed control that incorporates a novel use for crop residues.


3.Progress Report

This subordinate project formally commenced in December 2010, when funding was appropriated from North Central Sustainable Agriculture Research and Education (NC-SARE) through the University of Minnesota. The project involves primarily the development and demonstration of a new method for postemergence control of weed seedlings. An implement that propels grit under air pressures of about 75 pounds per square inch (psi) abrades small weed seedlings within corn rows, but leaves corn plants unharmed. The grit can be comprised of crop residues (for example, ground corn cobs or walnut shells) or organically-approved fertilizers (such as seed meals, crushed limestone, or gypsum). Expected progress of the subordinate project increases the likelihood of successful development of integrated sustainable crop production systems on organic farms. The subordinate project directly embraces novel weed control tactics, which is a main objective of the parent project. Preliminary tests using an analogue of the abrasive grit applicator were described in a manuscript submitted to the journal, Weed Technology, during the winter of 2011. The message of this manuscript can be summarized as follows: Season-long in-row weed control in corn is affected by two timely applications of grit, the first at the 1-leaf stage of corn, and the second at the 5-leaf stage of corn development. In such treatments, corn yields did not differ from those in hand-weeded check treatments. The Project Director organized a planning meeting in April 2011 that included four collaborating organic growers, a consulting engineer, a professor of weed science and a professor of agricultural engineering and his graduate student from SDSU, and an agronomist and two soil scientists from USDA. The graduate student’s thesis topic is the construction of a four-row grit applicator. A beta-test version of the applicator is anticipated for demonstration purposes by August 2011, with field trials to commence in spring 2012.


Last Modified: 10/20/2014
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