Abstract: A full-season field study was conducted near College Station, TX to determine the competitive interference of Palmer amaranth on cotton development, yield, and fiber properties and to measure Palmer amaranth development as influenced by intraspecific competition. Palmer amaranth densities ranged from 0 to 10 plants/9.1 m of row. Palmer amaranth decreased cotton canopy volume by 45% at 10 wk after cotton emergence (WAE) and cotton biomass by greater than 50% at 8 WAE at the highest density. Cotton yields decreased linearly from 13 to 54% for 1 to 10 Palmer amaranth plants/9.1 m of row. Cotton lint properties were not influenced by Palmer amaranth density. Palmer amaranth volume and individual biomass were not affected by intraspecific competition at any of the densities.
Nomenclature: Cotton, Gossypium hirsutum L. Delta and Pineland 50; Palmer amaranth, Amaranthus palmeri S. Wats #3 AMAPA.
Additional index words: Cotton biomass, interspecific competition, intraspecific competition, weed density.
Abbreviations: POST, postemergence; WAE, weeks after emergence.