Evaluating Ecosystem and Agronomic Services Provided by Companion Cropping in Hemp (Cannabis sativa L.)

Abstract

Hemp, Cannabis sativa L., was legalized in the United States in the 2018 Farm Bill for industrial production. While growing has boomed, profitable agronomic practices lag behind in the infant industry. Growers are specifically interested in weed and pest management strategies that do not impact yield or quality, as there are few herbicide and pesticide options for hemp, and they want agronomic practices to be sustainable or regenerative. Our research assesses the utility of companion cropping to address these needs. Companion cropping is a cultural management tactic within farming systems in which a secondary crop is planted with the main crop, offering an array of potential benefits and ecosystem services. Some of the possible benefits of companion cropping within hemp systems include weed control, additional food sources and habitat for beneficial insects, pest deterrence, increased crop productivity, soil health, and environmental resilience against stresses. To determine which companion crops are most suitable within cannabidiol (CBD) hemp production, we have analyzed the effects of intercropping five companions (basil, dill, cilantro, sage, and marigold, against a blank control) on: (i) companion plant yield and profit, (ii) weed competition, (iii) insect diversity, (iv) hemp biomass yield, and (vi) cannabinoid content. Results show that companion crops differentially and significantly impact weed cover and insect diversity, but do not significantly impact yield or cannabinoid content, with marigold and basil being the most promising. This means that growers can choose companion crops that fit their farm and equipment best without having to worry about a negative impact to quality and yield. Future studies will focus on implementation of companion cropping through on farm trials, an exciting and necessary next step to a sustainable future for cannabis production.