Industrial hemp yield and chemical composition as influenced by row spacing, fertilization, and environmental conditions

Abstract

Industrial hemp (Cannabis sativa L.) production is expanding in the United States, generating sustained interest in this multipurpose crop, though the optimal agronomic conditions (e.g., row spacing, planting density, and nutrient management) for maximizing fiber yield remain unclear in many regions. Key factors like row spacing not only affect resource utilization but also play a crucial role in weed suppression, especially in regenerative organic systems. This research at the Rodale Institute, Kutztown, PA, examined the effects of row spacing (19 cm narrow vs. 38 cm wide) and fertilization treatments (control, blood meal containing 12% N at 112 kg ha⁻¹ and 224 kg ha⁻¹, and compost at 60 t ha⁻¹) on yield and chemical composition of industrial hemp seed (cultivar: Canda) over two growing seasons (2019 and 2020). The narrow row spacing increased plant and stalk density, boosting bast fiber yield, while wider spacing promoted weed biomass due to reduced crop competition. Higher temperatures in the late growing season in 2020 led to 3.5 times increase in biomass yield and improved grain protein content. Principal component analysis indicated that compost influenced nutrient availability and heavy metal uptake more strongly than row spacing or blood meal treatments. Blood meal had limited effects, likely due to insufficient application rates, but showed promise for minimizing heavy metal uptake compared to compost. Optimal crop performance depends on the interaction between climatic conditions and agronomic practices. Selecting appropriate row spacing and nutrient sources is essential for enhancing hemp production while reducing input costs and minimizing environmental impact.