INTEGRATION OF ALLELOCHEMICALS WITH VARYING RATES OF HERBICIDES FOR ECONOMICAL WEED MANAGEMENT IN RAINFED WHEAT

Abstract

Allelopathic extracts can be used for weed management but are not preferred by the farmers due to low phytotoxicity. Phytotoxicity of allelopathic aqueous extracts may be synergized by the appropriate mixing with compatible herbicides at their economically lower and effective rates. The impact of aqueous extracts of sunflower and sorghum alone and in integration with the reduced doses of mesosulfuron plus iodosulfuron were examined to manage weeds in wheat under rainfed conditions. A field study was carried out during 2009-11 in a randomized complete block design. The treatments were hand weeding, mesosulfuron plus iodosulfuron at 14.4 g a.i. ha^-1, sorghum extract at 20 L ha^-1, sunflower extract at 20 L ha^-1, sorghum plus sunflower extracts each at 10 L ha^-1, mixtures of sorghum plus sunflower extracts with 3.6, 7.2 and 10.8 g a.i. ha^-1 of mesosulfuron plus iodosulfuron, and a control. The data exhibited greater than 80% suppression of weeds with hand weeding. Allelopathic extracts reduced weed density, fresh and dry weight of total weeds in the range of 25-58% while mesosulfuron plus iodosulfuron at 14.4 g a.i. ha^-1 controlled weeds by 58-65%. The mixture of extracts with 75% of the recommended rates of mesosulfuron plus iodosulfuron was comparable with its full rate. Regression analysis showed that 1 kg of weed biomass reduced 7.67 kg ha^-1 of wheat grain yield. Hand weeding exhibited the highest number of tillers per unit area and grains per spike. Allelopathic extracts integrated with mesosulfuron plus iodosulfuron at 10.8 g a.i. ha^-1 produced similar grain yield as obtained from the hand weeding and mesosulfuron plus iodosulfuron at 14.4 g a.i. ha^-1. Extracts mixed with mesosulfuron plus iodosulfuron at 7.2-10.8 g a.i. ha^-1 provided more net benefits as compared to the other treatments. It is inferred that sorghum and sunflower aqueous extracts integrated with 7.2-10.8 g a.i. ha^-1 of mesosulfuron plus iodosulfuron may be used to manage weeds in rainfed wheat for environmental safety.