Comparing Nutrient Management Strategies in Decoupled Aquaponics Systems for Growing Cannabis sativa

Abstract

Aquaponics is a system of aquaculture that uses waste produced by farmed aquatic animals to supply nutrients to a hydroponic system for growing plants. The growth of Cannabis sativa in aquaponics systems displays the potential for well-managed aquaponic systems to produce a variety of crops. A small, commercial-style aquaponic system was used to test how nutrient management techniques impact the growth of Cannabis sativa in a decoupled aquaponics system. Treatments included: a recirculating treatment using aquaponic system effluent plus nutrient supplementation (AqRN), a flow-through treatment utilizing aquaponic system effluent (AqFT), a flow-through hydroponic treatment supplemented with aquaponic effluent (10% by volume) (AqHydro), and a flow-through hydroponic control treatment (Hydro). Following a 13-week growing trial, flower buds were harvested, dried, and cured to determine yields from each treatment. Cured samples (3g) were sent to a lab for analysis of cannabinoids and terpenes.Results show growing hemp in aquaponics systems can provide comparable yields to hydroponic systems. No significant difference in yield existed between AqHydro, Hydro, and AqFT treatments. The AqRN treatment showed a significantly lower trimmed yield and plants showed signs of stress and nutrient deficiency approaching the end of the trial. The AqFT produced fewer overall terpenes than the other treatments and may benefit from micro-nutrient supplementation. The AqHydro and Hydro treatments showed no significant difference in water quality or yield. However, the AqHydro treatment consumed less water, indicating that supplementation with aquaculture effluent has the potential to significantly reduce the cost of fertigation in hydroponics systems.