Submitted to: Kenaf Association International Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: June 20, 2000
Publication Date: July 1, 2000
Citation: WEBBER III, C.L. WEED INTERFERENCE AND HERBICIDE RESIDUES WITH KENAF. KENAF ASSOCIATION INTERNATIONAL CONFERENCE PROCEEDINGS. 2000. P. 32. Technical Abstract: Kenaf (Hibiscus cannabinus L.) is produced as a fiber and feed crop. Despite ample information concerning the effectiveness of trifluralin and pendimethalin as preemergent herbicides for kenaf, there is no research investigating the possible presence of herbicide residues in kenaf plant tissues. The objectives of this research were to determine the effect of selected herbicides and weeds on kenaf yields, and to analyze the plant tissue for herbicide residues. A two-year field study was conducted at Lane, OK on a Bernow fine sandy loam. Trifluralin and pendimethalin were applied as preemergence herbicides at three rates (0.56, 1.12, and 2.24 kg ai/ha). The experiments also included a weed-free and a weedy-check treatment. Kenaf cultivar 'Tainung #2' was planted during May of each year and harvested at either 75 or 150 days after planting (DAP). Weeds reduced yields in the weedy-check at 75 DAP by 33%, and by 11% at 150 DAP. Ninety-one percent (1.8 mt/ha) of the yield reduction at 150 DAP was already present at 75 DAP. These results demonstrated that early (75 DAP) yield loss due to weed interference continued throughout the growing season, even though the percentage loss due to weeds decreased as full season (150 DAP) yields increased. All chemical analyses of kenaf plant tissue for trifluralin and pendimethalin residues at the three application rates, harvest dates, and years were below the detection limits of 0.02 ppm for trifluralin and 0.05 ppm for pendimethalin. These results will be an important consideration for herbicide registration of trifluralin and pendimethalin for kenaf as a livestock feed, animal bedding, or for any other use that may enter the food system.