Subsurface drip irrigation reduces weed infestation and irrigation water use while increasing inflorescence and cannabinoid yield in an outdoor tunnel Cannabis sativa L. production system

Abstract

Cannabis ( Cannabis sativa L.) has served as a valuable medicinal plant for thousands of years and is experiencing a resurgence in cultivation and research due to recent legal changes. However, the resource-intensive nature of cannabis cultivation, particularly water and energy demands, poses significant environmental challenges. Outdoor cultivation in a semi-controlled environment can reduce those energy demands but necessitates irrigation. Drip irrigation (DI) is the most commonly used irrigation method but is often criticized for its susceptibility to water losses through evaporation and the risk of surface runoff. Subsurface Drip Irrigation (SDI) provides a sustainable solution by minimizing evaporation losses while maintaining or increasing yields, thereby enhancing water use efficiency. In this study, we compared the effects of DI and SDI on weed infestation, total water usage, inflorescence yield, and water use efficiency of three CBD-rich cannabis chemotype III genotypes (Kanada, Terra Italia, FED) in an outdoor foil tunnel cultivation system. SDI resulted in a reduction of irrigation water usage by 18.6% compared to DI. Remarkably, weed dry biomass was reduced by 93.2% in SDI. Concomitantly, inflorescence yield increased by 5% and CBD concentration by 9%. Overall, the water use efficiency of inflorescence yield and CBD concentration was significantly higher in SDI than in DI. Our results indicated that implementing SDI instead of DI can significantly decrease irrigation water use and reduce weed infestation while increasing inflorescence and CBD yield, thus reducing the environmental challenges associated with cannabis cultivation.