Soil and weed management effects on floral hemp (Cannabis sativa L.) production and cannabinoid content

Abstract

AbstractMany floral hemp (Cannabis sativa L.) growers rely on tillage and black plastic mulch to prepare soil for transplants, warm the soil, and control weeds. However, plastic waste and its high cost to growers drive the need for research to assess alternative weed and soil management practices. Experiments were conducted at two Maine locations in 2021 and 2022 to compare cover crop soil and weed management systems on hemp production, cannabinoid concentrations, and yield. Experimental treatments included (1) tilled raised bed‐black plastic mulch, (2) biweekly cultivation, (3) no weed control, and (4) mowed no‐till mowed winter rye (Secale cereale L. Aroostook). Experimental sites received twice the 30‐year monthly average rainfall in July and September 2021 leading to poorer production versus typical 2022 long‐term average rainfall. Ice damage reduced winter rye biomass in 2022 at University of Maine Rogers Farm, leading to several significant year by location and year by weed management interactions. Hemp grown in the no‐till winter rye mulch developed more slowly, produced lower yields, and had higher weed densities than cultivated or black plastic mulch treatments. Plant size, yield, and cannabinoid content were generally equivalent where weeds were controlled. Raised bed‐black plastic soil and weed management were most effective under excessively wet conditions to reduce soil moisture and improve drainage. Cannabinoid concentrations did not increase under high weed pressure, but cannabinoid yield was influenced by flower production, which was significantly lower in the mowed rye mulch and control treatments. Blending raised bed production with efficient cultivation warrants research attention.