Development and Demonstration of a New Method of Physical Weed Control

Development and Demonstration of a New Method of Physical Weed Control

Summary

The propelled abrasive grit management (PAGMan) system was field-tested successfully in certified organic silage corn in 2013. PAGMan provided >80% weed control when measured at the end of the growing season, and its use maintained high silage yields.

The experiment was led by a PhD student from the Department of Plant Sciences, South Dakota State University. Results were disseminated through an oral presentation at the annual meeting of the Weed Science Society of America in February 2014. The abstract is available on the WSSA website, and the abstract and PowerPoint presentation are posted on the NC-SARE website. 

Objectives/Performance Targets

The four-row absrasive grit applicator was engineered and constructed in 2011 and 2012. The primary goal for 2013 was to field-test the implement on certified organic land.

Objectives were to examine the timing of grit abrasion events. These times corresponded to the 1-leaf, 3-leaf, and 5-leaf stages of corn development, as well as combinations of these times.

Success was determined by measurements of end-of-season weed control (compared to weedy checks) and maintenance of high corn yields (compared to hand-weeded checks).

A secondary objective was to subject our results to critical examination by other scientists, especially weed scientists, to help guage interest in the technique and, perhaps, expand the concept to other cropping systems.

Accomplishments/Milestones

Research during 2013 examined weed efficacy and crop yield of an integrated air-propelled abrasive corn-cob grit (for within-row control) and flame-weeding or cultivation (for between-row weed control) system at varying timings and frequencies in an organic corn crop at Morris, MN. Grit, flaming, cultivation, or grit + flaming, grit + cultivation, were applied as single (V1, V3, V5 corn growth stages), double (V1+V3, V1+V5, and V3+V5), or triple (V1+V3+V5) applications. A split-split-plot design with four replications, which included season long weedy and weed-free treatments, was used. Corn was harvested for silage yield in August and weed biomass (in-row and between-row) was determined.

Corn yield was increased over weedy plots (13,540 kg/ha) when grit was applied at V1 (40%), V3 (30%), and the combination of V1+V3 (42%). Grit application at V5 alone or in combination with between row methods did not influence yield. At V1, grit + cultivation increased yield over V1 grit alone by about 15%, whereas grit + flaming decreased yield by 15% when compared with grit alone. At V3, grit + cultivation increased yield over V3 grit alone by about 7% whereas grit + flaming reduced yield compared with grit alone.

Weed biomass within-row was reduced by 71% when grit was applied at V1, by 54% at the V3 application, and by about 80% when grit was applied at V5, V1+V3, V1+V5, V3+V5, and V1+V3+V5 compared with the season long weedy treatment (2940 kg/ha). At V1, grit + cultivation and grit + flaming reduced weed biomass by an additional 17 and 25%, respectively, compared with grit alone. Depending on treatment, other combinations increased control ranging from 3 to 26%.

These results indicate that abrasive corn-cob grit for in-row weed control can reduce weed biomass substantially. One application at V1 can increase corn yield. Additional treatments with or after the V1 treatment improved weed control and may increase yield. Waiting until V5 for grit application resulted in 80% in-row weed biomass reduction, however, because weed interference permanently stunted corn growth, there was no positive effect on corn yield.

Consequently, our current recommendation is to apply abrasive grit twice; first at the V1 stage, and again at either the V3 or V5 stage of corn development. Lastly, between-row flaming or between-row cultivation can be used to supplement in-row weed control with abrasive grit.

Impacts and Contributions/Outcomes

Contributions:

1. Forcella, F. 2013. Soybean seedlings tolerate abrasion from air-propelled grit. Weed Technology 27:631-635.

2. Erazo-Barradas M, SA Clay, and F Forcella. 2014. Grit application controls weeds in organic crop production. Weed Science Society of America Abstract 268.  http://wssaabstracts.com/public/22/proceedings.html

Impacts:

1. Article about the abrasive grit applicator will be featured in the July 2014 issue of Agricultural Research magazine.

2. The concept of using abrasive grit stimulated new weed horticultural research activities at the University of Illinois. This new research was published recently in a WSSA journal: 

Wortman SE. 2014. Integrating weed and vegetable crop management with multifunctional air- propelled abrasive grits. Weed Technology 28: 242-253.

• Soybean tolerates abrasive grit
• Illinois explores use of abrasive grit
• WSSA 2014 Presentation
• WSSA 2014 Abstract

Collaborators: