Department of Agronomy, Punjab Agricultural University, Ludhiana-141 004, India.
Effect of keeping weedy and weed-free for varying periods was studied in two American cotton genotypes (LH 886 and LH 900) during kharif 1989 and 1990 at the Punjab Agricultural University, Ludhiana. Weedy conditions for 60 days during first year and 45 days during second year affected significant reduction in seed cotton yield as compared to weedy for 30 days or weed-free. Weedy conditions resulted in decrease in plant height, number of monopodial and sympodial branches, bolls/plant and seed cotton yield. Weed-free throughout, though, gave highest seed cotton yield but was at par with weed-free upto 60 days after sowing. The critical period of crop-weed competition occurred between 45 and 60 days after sowing. The varieties tested did not differ in their suppressing effect on weeds.
