Effect of Nitrogen Fertilizer RATE and Herbicide on Industrial Hemp.

EFFECT OF NITROGEN FERTILIZER RATE AND HERBICIDE ON INDUSTRIAL HEMP. R. Anderson, P. Woosley, and T. Willian, Department of Agriculture, Western Kentucky University, Bowling Green, KY 42101.

Abstract

Industrial hemp (Cannabis sativa) is an old crop being reintroduced into certain states; thus, very little information is known about growing the crop domestically. This study was established to determine the optimal rate of nitrogen fertilizer application and the effects of herbicide application on crop growth and yield. The study utilized a split plot design with 4 treatments of nitrogen fertilizer rates (0, 78, 157, and 235 kg ha^-1); each treatment was replicated 4 times. Half of each treated plot was sprayed with pendimethalin herbicide at a rate of 2.8 L ha^-1. Data collected included stand counts at 34 days after planting (DAP), plant heights at 34 and 55 DAP, and stand counts, plant heights, fresh biomass, and seed yield at harvest (89 DAP). The addition of herbicide reduced stand counts at harvest, an average of 52% (P < 0.01) across treatments. Herbicide affected plant height at 34 DAP (P < 0.01), but not at 55 DAP or at harvest (P > 0.40). Nitrogen rate influenced both fresh weight (P < 0.01) and dry weight (P < 0.01); rates of 157 and 235 kg ha^-1 increased fresh weight and dry weight compared to the control. Seed yield was not affected by herbicide (P = 0.07); however N rate affected seed yield (P < 0.01). Over time plants were able to overcome the effects of herbicide treatment; therefore, herbicide did not have an effect on fresh weight or dry weight at harvest.