Growth and interaction of barnyardgrass (Echinochloa crus-galli) with cotton (Gossypium hirsutum).
Several weed-free and E. crus-galli competition periods were established in cotton cv. Acala SJ-2 field plots in Shafter, California, during 1988-89 on a sandy loam soil, to evaluate their influence on cotton yield and E. crus-galli seed production. When E. crus-galli was sprayed with fluazifop 3, 6, 9, or 12 weeks after cotton emergence, only plots sprayed at 3 weeks yielded as much cotton as weed free plots. E. crus-galli permitted to compete for 6, 9, 12, and 25 weeks reduced cotton yields an av. of 21, 59, 90, and 97%, resp. When E. crus-galli was sown into weed-free plots at 3, 6, 9, and 12 weeks after cotton emergence, a weed-free period of 9 weeks was required to prevent cotton yield reduction. Cotton in plots weed free for 3 and 6 weeks yielded an av. of 13 and 87% as much cotton, resp., as weed-free controls. E. crus-galli produced 15 to 85% as many seeds as weedy controls in plots weed free for less than 9 weeks and in plots where control was delayed for 9 and 12 weeks. Cotton grades were reduced because of grass in plots weed free for 3 and 6 weeks and in plots where E. crus-galli competed for 9 and 12 weeks.