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1 November 2002 Weed reproduction model parameters may be estimated from crop yield loss data
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Studies quantifying weed seed production as a function of weed density are expensive and difficult, and lack of these data is a common limitation in modeling weed population dynamics over time. Observed empirical and theoretical relationships between crop yield loss curves and weed seed production curves led us to the hypothesis that there should be a strong relationship between the shapes of these two curves. Data from literature sources were evaluated to test this hypothesis for hyperbolic curves and to determine if the data describing the crop yield loss caused by weeds could provide estimates of the shape parameter of a hyperbolic equation for describing density dependence in weed reproduction. For each of 162 data sets, a shape parameter (N50) and a scale parameter (U ) were estimated for an increasing hyperbolic model both for absolute crop yield loss as a function of weed density (N50YL, UYL) and for weed yield (either total biomass yield or seed yield) as a function of weed density (N50WY, UWY). N50YL was strongly correlated with N50WY across all data sets, with an apparent 1:1 relationship between the two. This relationship suggests that the shape parameter of the yield loss model may substitute for the shape parameter of a hyperbolic model describing the density-dependence of weed seed production. This substitution will be most useful in weed population modeling situations where data describing crop yield loss as a function of weed density are already available, but data describing weed seed production as a function of weed density are not available.

Nomenclature: barnyardgrass, Echinochloa crus-galli (L.) Beauv. ECHCG; black medic, Medicago lupulina L. MEDLU; catchweed bedstraw, Galium aparine L. GALAP; common cocklebur, Xanthium strumarium L. XANST; common ragweed, Ambrosia artemisiifolia L. AMBEL; corn poppy, Papaver rhoeas L. PAPRH; downy brome, Bromus tectorum L. BROTE; eastern black nightshade, Solanum ptycanthum Dun. SOLPT; field violet, Viola arvensis Murr. VIOAR; giant foxtail, Setaria faberi Herrm. SETFA; green foxtail, Setaria viridis (L.) Beauv. SETVI; hemp sesbania, Sesbania exaltata (Raf.) Rydb. ex A.W. Hill SEBEX; johnsongrass, Sorghum halepense (L.) Pers. SORHA; jointed goatgrass, Aegilops cylindrica Host AEGCY; kochia, Kochia scoparia (L.) Schrad. KCHSC; littleseed canarygrass, Phalaris minor Retz. PHAMI; redstem filaree, Erodium cicutarium (L.) L'Her. ex Ait. EROCI; round-leaved mallow, Malva pusilla L. MALNE; smooth pigweed, Amaranthus hybridus L. AMACH; spurred anoda, Anoda cristata (L.) Schlecht. NAVCR; velvetleaf, Abutilon theophrasti Medicus ABUTH; wild oat, Avena fatua L. AVEFA; wild poinsettia, Euphorbia heterophylla L. EPHHL; wild-proso millet, Panicum miliaceum L. PANMI; barley, Hordeum vulgare L.; chili, Capsicum annuum L.; dry bean, Phaseolus vulgaris L.; field pea,

Stephen R. Canner, Lori J. Wiles, and Gregory S. McMaster "Weed reproduction model parameters may be estimated from crop yield loss data," Weed Science 50(6), 763-772, (1 November 2002).[0763:WRMPMB]2.0.CO;2
Received: 26 November 2001; Accepted: 7 May 2002; Published: 1 November 2002

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