Author
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Kremer, Robert |
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Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract Only Publication Acceptance Date: 2/9/1998 Publication Date: N/A Citation: N/A Interpretive Summary: Technical Abstract: Productivity of many soils including the claypan soils typical of mid- Missouri uplands can be sustained using improved cover crop management. Cover crops established on these soils for weed management are also of important economic and environmental interest to many farmers. Inclusion of weed-inhibiting microbial agents with allelopathic cover crops could optimize weed control and reduce herbicide use. The objective was to evaluate several cover crops for weed control alone and combined with soil- applied deleterious rhizobacteria (DRB). At least eight weed species comprised the seedbank at field sites with densities ranging from 1000 seeds per m**2 (10-cm depth) for velvetleaf (Abutilon theophrasti) to >4000 seeds per m**2 for giant foxtail (Setaria faberi). In early June and mid- August 1996 and 1997, barley, rye, and wheat covers with or without DRB reduced total weed biomass >90% compared to weedy checks. Brassica species s(canola, rape, and green mustard), annual ryegrass, and sweet clover reduced weed biomass by 30 to 80% without DRB and by 40 to 95% when combined with the soil-applied DRB. DRB genetically marked for antibiotic resistance were detected on roots of cover crops and established high populations in soil that presumably colonized the periodically-germinating weed seedlings and contributed to subsequent weed growth suppression. Rhizosphere colonization by DRB varied among cover crops (10**2 - 10**6 cells per cm root) indicating specificity, useful in selecting of cover crops for establishing high DRB densities in soil. Results suggest that integration of two or more approaches may enhance the efficacy of biological weed management. |