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Submitted to: Weed Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 2/7/1999 Publication Date: N/A Citation: N/A Interpretive Summary: Despite extensive efforts to eliminate them from agricultural lands, weeds continue to plague farmers. An important characteristic that allows many weeds to survive is their ability to produce seed under adverse conditions and the ability of those seeds to survive in the soil from year to year. The weed seed reserve in the soil is commonly referred to as the weed seed bank. Since weed control practices influence the ability of weeds to produce seeds and the survival of those seeds, it is important to understand the influence of different weed control practices on the weed seed bank. The objective of our research was to improve the understanding of effects of weed control practices on the weed seed bank, weed control, and crop yields under high and low weed pressures. We found that the affects of weed control practices on weed populations and crop yields were influenced by initial weed density, species composition, and weather conditions. Based on the results of this research, a wide range of weed control options were consistently effective when weed densities were low. At high weed populations, weed control and crop yields were more sensitive to weather conditions and mechanical weed control operations rapidly lost effectiveness. Thus, it is difficult to make general statements on the effects of weed control practices on weed populations and crop yields. When farmers consider changing their weed control practices they need to consider expected weed densities and species composition, crop rotation plans, and management skills. Technical Abstract: Weed control practices affected the weed seed content of the soil, weed seedling populations, and corn and soybean yields in two 4-year field experiments. When the initial weed seed density was high, giant foxtail seed numbers in the soil declined rapidly under weed-free conditions. Changes in seed densities when initial densities were low varied over years. Mechanical and chemical control treatments had variable effects on weed seed numbers over the course of the experiment. Weed seed numbers and weed densities were sometimes greater if herbicides were banded, but crop yields were similar to full-rate herbicides in both experiments in all years. When the initial density was low, giant foxtail seed numbers in the soil increased over the course of the experiment regardless of the weed control treatment. Densities of broadleaf seeds decreased under the same conditions. Also when initial weed densities were low, weed control and crop yields were less sensitive to weed control practices than at high weed densities. Weather factors that influenced treatment efficacy had a major affect on weed populations and crop yield responses to the weed control treatments over years. The interactions of weed control practices, weed populations, and crop yields were complex. Initial weed density and species composition interacted with weed control treatments and weather patterns to generate the results observed. |
