ALLELOPATHIC IMPACT OF SORGHUM AND SUNFLOWER INTERCROPPING ON WEED MANAGEMENT AND YIELD ENHANCEMENT IN COTTON

The study was carried out at Cotton Section, Agriculture Research Institute, Tandojam Pakistan during kharif (Summer) 2010 and 2011. The soil of experimental area was clay loam which according to USDA system belongs to Order Aridisols and Sub-group Typic Camborthids. The treatments comprised of No weeding (Control), Interculturing twice (30 and 60 days after sowing: DAS), Herbicide Dual Gold 960 EC (S-metolachlor) @ 2.5 L ha^-1 (Preemergence), Cotton+Sorghum Intercropping (1:1 row proportion), Sorghum Sole, Cotton+Sunflower Intercropping (1:1 row proportion) and Sunflower sole. Seeds of cotton variety Sindh-1, Sorghum dwarf variety MR-Buster and Sunflower hybrid Hysun-39 were sown in respective treatments. The analysis of variance showed that Intercropping of sorghum and sunflower with cotton suppressed weeds significantly by 62.4 and 59.6 %, respectively and significantly enhanced growth and yield traits of cotton, particularly seedcotton yield as compared to No weeding. Interculturing twice caused markedly higher (67.5 %) reduction of weeds and produced significantly higher seedcotton yield (4011.65 kg ha^-1) over No weeding and rest of the treatments. Application of Dual Gold 960 EC also demonstrated substantial weed control efficiency (53.4 %) and considerably enhanced seedcotton yield against No weeding. However, Intercropping of sorghum and sunflower with cotton produced noticeably higher total crop productivity (4285 and 4270 kg ha^-1), respectively as compared to seedcotton yield obtained in Interculturing and Dual Gold 960 EC plots (4011 and 3747 kg ha^-1). The highest similar land equivalent ratio (LER) 1.80 and price equivalent ratio (PER) 1.79 were obtained in Cotton+Sorghum and Cotton+Sunflower intercropping systems against No weeding, whereas equal 1.26 LER and 1.29 PER were recorded in intercropping of both crops as compared to Interculturing twice. Intercropping of both sorghum and sunflower in cotton was found most economical, effective and eco-friendly weed management strategy for producing higher net benefits than rest of the treatments. Interculturing due to shortage and higher costs of labour was found economically impractical, while the application of herbicides now-a-days is being discouraged due to causing environmental pollution and human health hazards, and also negatively affecting nutritive value of crops.