Herbicide Effects on Industrial Hemp (Cannabis sativa L.) Seed Production.

A Study was conducted in 2015 to evaluate herbicide effects on industrial hemp (Cannabis sativa L.). This study took place at the Western Kentucky University Agricultural Research and Education Complex in Bowling Green, KY and at the University of Kentucky Spindletop Research Experiment Station in Lexington, KY. A mixture of Italian cultivars used primarily for fiber production were used in Bowling Green. ‘Finola’, a cultivar utilized in industrial hemp seed production was used at the Lexington location. The industrial hemp was planted in June and harvested in September of 2015. Five pre-emergent herbicides and six post-emergent herbicides were evaluated. Significant differences were observed among herbicide treatments. Hemp seed yields ranged from 45 - 1,137 kg/ac.  Pre-emergent herbicides resulted in higher seed yields in Bowling Green while post-emergent herbicides resulted in higher seed yields at Lexington. The pre-emergent herbicide, pendimethalin and post-emergent herbicide, MSMA were not significantly different from the weed-free check at both locations. Mesotrione applied as a pre-emergent and the post-emergent herbicide trifloxysulfron resulted in significantly lower seed yields at both locations. Should industrial hemp become legal to produce in the U.S., pendimethalin and MSMA could be viable herbicide options for weed control.