Feasibility of medicinal cannabis cultivation in outdoor conditions using municipal reclaimed water

Abstract Increasing pressure on freshwater resources represents a major challenge for sustainable agricultural production in arid and semi-arid regions. In this context, the use of treated wastewater in agriculture may enhance environmental sustainability and economic efficiency. This study evaluated the yield and safety of outdoor cannabis cultivation irrigated with reclaimed domestic wastewater in an arid Patagonian environment (Argentina). Key metrics included soil and water quality, flower and cannabinoid yield, and chemical and microbiological safety. Soil and water quality were adequate in terms of physicochemical parameters. Escherichia coli in irrigation water at the time of tank filling was 1,700 ± 733 MPN/100 mL. Irrigation was initiated at these concentrations, and E. coli levels declined during subsequent storage in tanks, reaching values below 1,000 MPN/100 mL after approximately 10 days, consistent with the World Health Organization guideline for unrestricted agricultural reuse. E. coli and total coliforms were absent in leaves, flowers, and derived products (herbal oils). Potentially hazardous heavy metals (As, Cd, Co, Cr, Cu, Ni, Pb, and Zn) did not show systematic accumulation in the system. Concentrations in flowers and oils were generally below regulatory standards for edibles; however, Pb levels in dried flowers exceeded established regulatory limits. Dried flower yields were approximately 267.77 ± 34.99 g/plant. Cannabinoid concentrations ranged from 7–14%, comparable to values previously reported for these varieties when cultivated indoors. Overall, the results support the potential of reclaimed wastewater as an irrigation alternative in arid regions, although continued monitoring of contaminants is essential to ensure product safety and regulatory compliance.