Industrial Hemp Root Length Density and Distribution under Polyethylene Mulch with Drip Irrigation

Delineating the depth and extent of the industrial hemp (Cannabis sativa L.) root zone assists with proper irrigation management and minimizes nutrient leaching. The objective of this 3-year field study was to measure root distribution and root length density of industrial hemp cultivars produced for cannabinoids grown under polyethyl-ene mulch with drip irrigation. Root length density (RLD) was measured from 75-cm -deep soil cores obtained during vegetative growth, at early bloom, and at flower harvest. Cores were taken in-row and 15 cm to the side of each plant. In addition to root cores, the trench profile method was used during 2020 to observe in situ gross root architecture of a direct-seeded cannabinoid cultivar. RLD was significantly greater in the 0-to 30-cm soil depth and dropped dramatically below 30 cm; RLD was not significantly affected by cultivar. These findings suggest that the effective root zone depth for industrial hemp cul-tivars produced for cannabinoids is 0 to 30 cm and that the cultivars tested in this study do not differ in root system size or location.