WEED MANAGEMENT AND YIELD IMPROVEMENT IN COTTON THROUGH ALLELOPATHIC MULCHES OF SORGHUM AND SUNFLOWER STRAW

Weeds are the major biotic constraints reducing crop yield. the injudicious and indiscriminate use of herbicides has created environmental pollution and human health hazards. manual methods are expensive. allelopathy has emerged as an environment-friendly and effective approach for weed management in field crops. sorghum and sunflower plants possess many allelopathic compounds with phytotoxic potential. weeds can be controlled effectively and use of herbicides can be minimized through utilizing allelopathic properties of such plants. a field study was carried out at cotton section, agriculture research institute, tandojam pakistan during kharif (summer) 2010 and 2011. the experimental treatments comprised of mulches of sorghum and sunflower straw (10 and 15 t ha^-1, respectively, interculturing twice (at 30 and 60 days after sowing: das), herbicide dual gold 960-ec (s-metolachlor) @ 2.4 kg a.i. ha^-1 and control (weedy check). the results indicated that all the levels of sorghum and sunflower mulches resulted in substantial suppression of weeds and enhanced seed cotton yield as compared to control (weedy check). sunflower and sorghum straw as mulch (15 t ha^-1) exhibited strong allelopathic properties with efficient weed control (67.5 and 67.0 %, respectively), seedcotton yield (3953.6 and 3938.3 kg ha^-1, respectively) and net benefits (rs. 222090 and rs. 176527 ha^-1, respectively). interculturing twice resulted in 69.0 % weed control with 3971 kg ha^-1 seedcotton yield and rs. 211390 ha^-1 net benefit as compared to control. therefore, use of sunflower straw as mulch was found economical for weed control and enhancing cotton yield whereas, sorghum mulch and interculturing were found less or uneconomical due to highest costs involved in both treatments.