Wheat (Triticum aestivum) yield response to henbit (Lamium amplexicaule) interference and simulated winterkill

No-till production systems coupled with decreased use of soil residual herbicides has led to increased populations of winter annual weeds. Therefore, research was conducted to quantify the effect of henbit interference and crop stand loss on soft red winter wheat grain yield and grain volume weight. The main-plot effect consisted of weed-free versus weedy plots. The subplot effect was winter wheat stand loss treatments of 0, 20, 40, 60, 80, and 100%. Henbit interference did not affect test weight; however, test weight decreased as percentage of stand loss increased. Henbit did not reduce crop yield at 18 plants/m(2); however, at 82 and 155 plants/m(2), crop yield was reduced 13 and 38%, respectively, when averaged across all stand loss treatments. Yield estimates based on wheat tiller or spike density decreased linearly as crop stand loss increased. Our results indicated that henbit interference coupled with crop stand loss may significantly decrease crop yield and profitability of wheat production systems. Nomenclature: Sethoxydim; henbit, Lamium amplexicaule L. #(3) LAMAM; winter wheat, Triticum aestivum L. 'Ernie', 'Roane'. Additional index words: Weed competition, yield loss, winterkill.