Determination of critical period of weed on yield components of cotton in cotton fields of Iran
2004
Atri, Ali Reza | Salimi, Homeira
In order to determinate the critical period of weed control in cotton( Gossypium hirsutum L.), an experiment was carried out in Varamin Research Center during 2000 – 2001 years The experiment was conducted in randomized complete block design with 14 treatments applied in two series. In the first series, weeds competed with cotton in different phonological stages of cotton (production of 1 and 5th true leaf stage, 1,3,5th reproductive branches and production of brown flower) and through the growing season. In the second series, weeds were controlled in above stages through out the growing season. Results showed that the height of cotton, number and length of branches, number of bolls and cotton yield were affected by weed competition. The critical period of weed control began from production of the first reproductive branch to production of brown flower on cotton in the first year. The critical period began sooner due to drought stress in second year and the first critical period began at the 5th leaves stage. Dominant weeds in the experiment included Amaranthus retroflexus L., A. viridis L., A. blitoides S.Watson, Portulaca oleracea L., Echinochloa crus – galli L. P.Beauv., Cyperus rotundus L., Sorghum halepense (L.) Pers.
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