Is combination ratio an important factor to determine synergistic activity of allelopathic crop extract and herbicide?
2013
Dilipkumar, M. (Malaysian Agricultural Research and Development Inst., Kelantan (Malaysia)) | Chuah, T.S. (University of Malaysia Terengganu (Malaysia). Dept. of Agro-technology)
Use of allelopathic crop water extracts in combination with herbicide for weed control in crop fields is well recognized. However, studies on joint action of allelopathic crop water extracts and herbicides using established models are still scanty. Addressing this need, the present study investigates the joint action of extracts of sunflower leaves and selected herbicides on shoot emergence and seedling growth of barnyardgrass (Echinochloa crus-galli) under laboratory conditions using the Additive Dose Model (ADM). ED50 (rate that causes 50% inhibition) from the dose-response curves for the sunflower leaf extracts or herbicides applied alone or in mixtures of fixed ratios were determined. The results of ADM analysis demonstrated synergism for both combinations, but the synergistic effects of pretilachlor and sunflower leaf extracts mixture was 10% stronger than mixture of thiobencarb and sunflower leaf extracts. The degree of synergism increased progressively with the increased ratio of sunflower leaf extracts: herbicide, but antagonism was evident at the lowest ratio of sunflower leaf extracts: herbicide. The results of this study have revealed that, the ratio of allelopathic crop water extracts in combination with herbicide is an important factor in influencing the potency of phytotoxic activity.
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