WEED POPULATIONS AS RELATED TO CONSERVATION TILLAGE AND REDUCED HERBICIDE MANAGEMENT SYSTEMS: MISSISSIPPI DELTA MANAGEMENT SYSTEMS EVALUATION AREA

Authors: Bryson, Charles; Hanks, James

Submitted to: American Chemical Society Symposium Series
Publication Type: Book / Chapter
Publication Acceptance Date: 7/1/2002
Publication Date: 3/1/2004
Citation: Bryson, C.T., Hanks, J.E. 2004. Weed populations as related to conservation tillage and reduced herbicide management systems: Mississippi Delta Management Systems Evaluation Area. In: Nett, M.T., Locke, M.A., Pennington, D.A., editors. American Chemical Society Symposium Series 877. New York, NY: Oxford University Press. pp. 204-217.

Interpretive Summary: Despite current knowledge of weed control methods, cumulative weed losses exceed $4.1 billion annually in the United States. The Mississippi Delta Management Systems Evaluation Area (MSEA) was established to improve water quality and incorporate safe and effective innovative agricultural practices. Over a 5-year period, weed population shifts were detected in conservation tillage cotton and soybean. Most weed populations were lower than at the initiation of the study in the reduced-tillage cotton and soybean, possibly because a hooded sprayer or genetically manipulated, herbicide-resistant crops were used. These results are encouraging for farmers, because most weed species were effectively controlled with less tillage. However, a few woody species (e.g. bigroot morningglory, horsenettle, etc.) populations increased in the reduced-tillage crop areas, regardless of the use of these management technologies.

Technical Abstract: Over a 5-year period, weed population shifts were detected in conservation tillage cotton (Gossypium hirsutum L.) and soybean [Glycine max (L.) Merrill] at the Mississippi Delta Management Systems Evaluation Area (MDMSEA) Deep Hollow (DH) site near Sidon, Leflore County, MS. At DH, plant populations were monitored to determine plant species composition, population levels, and weed shifts in cropland areas including conventional, conservation tillage, and reduced herbicide management systems. Plant species composition was determined for non-cropland areas including grass filter strips, field borders, riparian zones, and in and around the watershed lake. The number of weed species and number per species were greater in conservation tillage than in conventional planted cotton and soybean in early season. Four primary types of weed shifts were detected in reduced input cotton and soybean production systems at DH: 1) some weed populations decreased in both crops; 2) other weed populations increased in both crops; 3) some weed populations increased initially and then decreased; and 4) other weed population increased in one crop while remaining constant or decreasing in the other crop. Most weeds were effectively controlled with the use of a hooded sensor-sprayer and transgenic crops.