Research was conducted to characterize the phenology of common lambsquarters growth parameters as influenced by climatic variation among years. Treatments included soybean or corn grown alone, common lambsquarters with soybean or corn, and common lambsquarters grown alone. Common lambsquarters leaf area and plant height phenology differed among years and was variable within treatments. Conversely, crop leaf area and plant height phenology did not differ among years and was less variable within a treatment than common lambsquarters. Weed relative leaf area and relative volume differed among years because of differences in crop and common lambsquarters leaf area and plant height phenology. Differences in common lambsquarters relative leaf area and relative volume among years may explain differences in previously reported crop yield responses to weed infestations between sites and years. Although common lambsquarters relative leaf area and relative volume differed among years, variability as indicated by regression coefficients of determination was also high within year and treatment. Crop leaf area and plant height phenology were well described by regression equations, with r2 values greater than 0.68. Therefore, low coefficients of determination for relative leaf area and relative volume models were attributed to variability in common lambsquarters within a treatment.
Nomenclature: Common lambsquarters, Chenopodium album L. CHEAL; field corn, ‘Dekalb DK493SR’, Zea mays L.; soybean, ‘Asgrow XP19505RR’ and ‘AG2101RR’, Glycine max L. Merr.