Author
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Teasdale, John |
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Submitted to: Weed Science
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 5/1/2000 Publication Date: N/A Citation: N/A Interpretive Summary: Mulches of organic materials on the surface of soil can play an important role in controlling weeds. However, we do not understand what characteristics of mulches are most important for weed control. This research compared seven mulches that had a wide variety of physical characteristics including bark chips, corn stalks, rye straw, crimson clover stems, hairy vetch residue, oak leaves, and strips of landscape fabric. We found that all mulches suppressed small-seeded weeds more than large- seeded weeds. This suggested that weed emergence was controlled by the availability of seed reserves to nourish seedlings as they grow through mulches. The physical characteristics that were most important to preventing weed emergence were the number of layers of mulch material and the amount of empty space within the mulch. These characteristics essentially determine how long a seedling can survive on its seed reserves before it must emerge into sunlight. Equations were developed that will permit prediction of weed emergence based on estimates of mulch quantities. This research will contribute to weed management models that allow growers to determine optimum weed control tactics. Technical Abstract: Mulches or organic residues on the soil surface are known to suppress weed emergence but there is little research that describes the quantitative relationships between emergence and mulch properties. A theoretical framework for describing the relationships among mulch mass, area index, height, cover, light extinction, and weed emergence is introduced. This theory is applied to data from experiments on emergence of four annual weed species through mulches of selected materials applied at six rates. Mulch materials, in order from lowest to highest surface area to mass ratio, were bark chips, corn stalks, rye, crimson clover, hairy vetch, oak leaves, and landscape fabric strips. The order of weed species sensitivity to mulches was redroot pigweed>common lambsquarters>giant foxtail>velvetleaf regardless of mulch material. The success of emergence through mulches was related to the capacity of seedlings to grow around obstructing mulch elements under limiting light conditions. Mulch area index was a pivotal property for quantitatively defining mulch properties and understanding weed emergence through mulches. A two-parameter model of emergence as a function of mulch area index and fraction of solid mulch volume reasonably predicted emergence across the range of mulches investigated. |
