Author
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Kremer, Robert |
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Submitted to: International Symposium on Biological Control of Weeds
Publication Type: Proceedings Publication Acceptance Date: 7/9/1999 Publication Date: N/A Citation: N/A Interpretive Summary: Field trials were conducted in Missouri to determine if combinations of non-chemical weed control methods could effectively reduce weed infestations and provide acceptable grain yields of soybean. Conventional crop production relies heavily on herbicides to control weeds, resulting in contamination of water and development of herbicide-resistant weeds. Herbicide-resistant crops are not a solution due to their expense, require use of more herbicides, and development of more herbicide-resistant weeds. Biological control with natural organisms suppresses weed growth but only affects specific weeds when fields typically have many different weeds infesting a crop. Cover crops, certain plants seeded to protect soil during periods when grain crops are not present, also suppress weeds by releasing natural chemicals from roots and dead vegetation into soil to inhibit weed seedling growth. By combining biological control (certain bacteria applied dto soil) and cover crops, we enhanced weed growth inhibition and soybean yielded similar to those grown conventionally. Cover crops promoted the growth of biological control bacteria in soil so that weed seedlings were attacked as they germinated and emerged. Results are important to producers because novel non-chemical weed management approaches can be developed for practical use in crop fields that eliminate or reduce reliance on herbicides. Technical Abstract: Development and rapid acceptance of biological weed control are challenged by factors limiting the spectrum of activity, efficacy, and reliability. Effectiveness of biological control may be demonstrated best as a component in an overall biological weed management system. Cover crops as components of biological weed management can be used for integrating biological control agents by promoting their establishment in soils for attack of wee seedlings prior to planting the main crop. The objective of this study was to evaluate several cover crop species alone and integrated with soil borne deleterious rhizobacteria (DRB) for weed control potential. Cereal grain cover crops reduced weed biomass by 90% compared to weedy checks. Brassica cover crops and sweet clover (Melilotus officinalis) reduced weed biomass to a greater extent when combined with soil-applied DRB. DRB were detected on roots of cover crops and established on roots of adjacent weed seedlings sfor subsequent growth suppression. In 1998, soybean (Glycine max) planted in several cover crop residues without herbicide yielded higher than weedy checks and equivalent or higher than conventionally grown soybean. Weed suppression was further enhanced when DRB were included. Integration of nonchemical weed control methods will potentially reduce herbicide use and enhance efficacy of biological weed management. |
