Submitted to: Weed Technology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/8/2010
Publication Date: 2/16/2011
Citation: Handiseni, M., Brown, J., Zemetra, R., Mazzola, M. 2011. Herbicidal activity of Brassicaceae seed meal on wild oat (Avena fatua), Italian ryegrass (Lolium multiflorum Lam.), Redroot pigweed (Amaranthus retroflexus L.) and Prickly lettuce (Lactuca serriola). Weed Technology. 25:127-134. Interpretive Summary: Fueled by consumer demand and innovative research, organic crop production is thriving, but sustainable methods of weed management remain a significant challenge. Effective weed control measures in organic production systems generally are lacking. Weed control typically relies on repeated cultivation during the growing season, a practice which degrades soil structure and can lead to loss of organic matter from the production system. Brassicaceae seed meals are a readily available waste product of oil extraction processes, including bio-fuel production, that possess promise as an alternative weed control soil amendment. Seed meal from the plants white mustard, oriental mustard and canola were evaluated for the potential to suppress various broad leaved and grassy weed species. The relative effectiveness of these seed meals varied with the plant source, application rate and the target weed species. In addition, denaturing seed meals by exposing the material to high heat commonly reduced or eliminated the weed control properties of these materials. Among those tested, white mustard seed meal appeared to possess the greatest weed control potential. The herbicidal effects of the mustard seed meals could offer growers a new option for weed control, particularly in organic production systems. In a real life practical situation it would perhaps seem feasible to treat soils with a blend of white mustard and oriental mustard seed meals to achieve optimal control of both grassy and broad leaved weeds.
Technical Abstract: There is an on-going need for the development of sustainable methods of weed control in crop production systems. Studies were conducted to evaluate the efficacy of different Brassicaceae seed meals and application rates on the emergence of several weed species including wild oat, Italian rye grass, prickly lettuce and pigweed. Sinapis alba ‘IdaGold’, Brassica juncea ‘Pacific Gold’ and Brassica napus ‘Dwarf Essex’ seed meals were used with or without a functional myrosinase enzyme. Seed meal amendments reduced weed seedling emergence by between 7-19%, 15-22%, 50-65% and 50-64% in Italian rye grass, wild oat, prickly lettuce and pigweed, respectively, at application rates of 1-2 Mt ha-1. Dry weed biomass was reduced by between 55-77% and 63-79% for prickly lettuce and pigweed, respectively, at seed meal application rates of 1-2 Mt ha-1. Intact S. alba seed meals applied at a rate of 2 Mt ha-1 significantly reduced weed seedling emergence and weed dry biomass compared to intact B. napus seed meal amended treatments. B. juncea showed significantly better herbicidal efficacy on the grassy weeds than S. alba which was most effective in controlling broadleaf weeds. In all instances, a 1 Mt ha-1 application rate of either B. juncea or S. alba exhibited greater herbicidal effect relative to a 2 Mt ha-1 application rate of B. napus seed meal. These results demonstrate that all glucosinolates are not equal in herbicidal effects. The herbicidal effects of the mustard seed meal could offer vegetable growers a new option for weed control, particularly in organic production systems. In a real life practical situation it would perhaps seem feasible to treat soils with a blend of B. juncea and S. alba seed meals so that both grassy and broad leaved weeds can be effectively controlled.