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LOGO: Journal of Cotton Science


Cotton Yield Loss Potential in Response to Length of Palmer Amaranth (Amaranthus palmeri) Interference

Authors: A. W. MacRae, T. M. Webster, L. M. Sosnoskie, A. S. Culpepper, and J. M. Kichler
Pages: 227-232
Weed Science

Field studies were conducted near Ideal, GA in 2006 and 2007 to determine the influence of simulated delayed emergence of Palmer amaranth at several densities on cotton yield and weed growth. Palmer amaranth plants in the 6- to 8-leaf stage were transplanted at five densities (ranging from 0 to 10 plants per 6.1 m row-1) and four time intervals defined by cotton leaf stage (3-, 8-, 12-, and 17-leaf cotton). Prior to harvest, Palmer amaranth biomass was removed from the plots and quantified, Palmer amaranth seed production measured, and cotton yield determined. When Palmer amaranth plants were transplanted in 3- or 8-leaf cotton, cotton yield was reduced approximately 6% for every Palmer amaranth per 6.1 m of row, with a maximum cotton yield loss of 60%. In contrast, there was no effect of Palmer amaranth density on cotton yield when Palmer amaranth established at the 12- and 17-leaf stages of cotton. Maximum Palmer amaranth biomass, averaged over all densities, was achieved when Palmer amaranth was established at the 3- and 8-leaf stages of cotton (9,190 kg ha-1), while Palmer amaranth biomass from plants established at the 12- and 17-leaf stages of cotton was reduced 73%. Palmer amaranth seed production per plant ranged from 61,000 when transplanted at the 3-leaf cotton stage to 14,000 seeds per plant for Palmer amaranth transplanted at the 17-leaf cotton stage. To avert cotton yield loss, Palmer amaranth interference should be eliminated prior to the 12-leaf stage of cotton; later-emerging plants may not affect cotton yields, but will replenish the soil seedbank.