Fish Effluent as a Source of Water and Nutrients for Sustainable Urban Agriculture

Integrating urban agriculture with aquaculture can reduce the use and cost of water, competition for water, chemical fertilizers, and environmental impact of discharging nutrient-rich agricultural water into fresh and saltwater bodies. In addition, aquaculture in cities can directly benefit human health by providing a local source of lean protein. Despite the potential advantages, few studies have demonstrated the feasibility and production advantages of using aquaculture wastewater to fertigate specialty crops in an urban environment. Therefore, we grew four spring crops (bok choy, tatsoi, radish, turnip) and two fall crops (pole beans, sugar snap peas) in nutrient-rich effluent from fish aquaculture versus well or municipal water to evaluate whether the effluent improved soil fertility and crop production. The fish effluent resulted in changes to the soil through an increase in pH and potassium and to crop production through a 9.1% increase in the number of pole beans (mass of beans also trended toward significance). The soils we used were relatively nutrient-rich prior to the application of the fish effluent, which may be responsible for the limited impact, and differences may be more apparent in acidic and nutrient-poor soils or when fertigation is used over a longer duration.