Field studies were conducted to use the water extracts of allelopathic crops (sorghum, sunflower and brassica) for reducing glyphosate rate for controlling purple nutsedge in cotton. Crop water extracts (12 and 15 Lha−1) in different combinations were tank mixed with reduced rate of glyphosate by 67% (767 g a.e. ha−1) of the label rate (2.3 kg a.e. ha−1) and sprayed as directed post emergence at 40 days after sowing (DAS). Purple nutsedge density was decreased by 59 to 99% and dry weight by 66 to 99% as compared to control, when different crop water extracts were used in combination with reduced rate of glyphosate. The higher rates of crop water extracts (15 L ha−1) significantly reduced the growth of purple nutsedge than lower rates (12 L ha−1). Seed cotton yield in these treatments was comparable to herbicide applied at recommended rates. These findings suggest that herbicide (glyphosate) rate can be reduced by 67%, when tank mixed with allelopathic crop water extracts. The results indicate great scope for evolving weed control strategies, based on natural plant extracts in the field.
Allelopathy, crop water extracts, cotton, Cyperus rotundus, glyphosate
