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Influence of Planting Depth and Application Timing on S-metolachlor Injury in Sesame (Sesamum indicum L.)

Sperry, Benjamin P., Ferrell, Jason A., Leon, Ramon G., Rowland, Diane L., Mulvaney, Michael J.
Weed technology 2016 v.30 no.4 pp. 958-964
Sesamum indicum, application timing, growth retardation, metolachlor, plant damage, plant establishment, planting depth, seed yield, seedling emergence, weeds, Florida
Two experiments were conducted in 2015 at multiple locations in Florida to evaluate the effects of planting depth and application timing on S-metolachlor injury in sesame. In both studies, sesame responded negatively to increases in S-metolachlor rate. Altering sesame planting depth did not provide increased safety to PRE S-metolachlor applications. Sesame establishment declined with increased planting depth, likely because of the physical inability of the small seed to emerge from the 3.8-cm depth. Delaying applications of S-metolachlor by 3 or 6 d after planting (DAP) consistently improved sesame establishment. Applications 3 and 6 DAP resulted in 89 to 92% seedling emergence at 2 wk after planting (WAP), relative to 55 to 63% emergence when S-metolachlor was applied the day of planting (0 DAP) or 3 days before (−3 DAP), respectively. Applications 3 DAP resulted in 21 and 2% plant stunting when evaluated 3 and 6 WAP, respectively, whereas all other timings caused 25 to 51% stunting. Yield was reduced 22 and 33% by the −3 DAP and 0 DAP application timings, respectively, whereas no reduction in yield was observed by the delayed application timings. Therefore, delaying applications of S-metolachlor by 3 to 6 days will likely result in improved sesame seedling establishment and total seed yield. Nomenclature: S-metolachlor; sesame, Sesamum indicum L. ‘S38’.