Unlike other agricultural techniques that focus on a single product, aquaponics growers must consider both the fish and the plants when altering the conditions of the system.
Aquaponic systems are often described as their own ecosystems. Everything from the types of organisms in the system to the bacteria breaking down waste impact the productivity and success of the system.
Fish meal is the major source of nutrients in the entire system. What the fish are fed, and how much, plays a role in determining which nutrients will be available for the plants further down the line.
“(The fish meal) will break down into the fundamental components of the fertilizer, which will then be broken down further by beneficial bacteria in the system,” says Trevor Kenkel, owner of Springworks aquaponics farm in Lisbon. “It will go on to then generate the major macronutrients for the plants, but also the micronutrients as well.”
Kenkel said they also monitor the amount of food they feed the fish to prevent excess nutrients in the system.
“The amount of nutrients that are thrown off out of a system is really significant, and it’s so concentrated,” he said. “If we weren’t running a system to capture this afterward, you would either be dumping those into a local ecosystem, or you’d have to find some other way to treat them, which can be very expensive.”
Managing the greenhouse environment can also be difficult, particularly in Maine. Growing produce in the summer and winter is very different, Kenkel said.
Springworks’ greenhouses have lights that supplement the sun on cloudy, gray days. Additionally, a system helps control the temperature within the greenhouses.
Paul Brown, a professor at Purdue University who studies aquaponics, said many factors are involved. For instance, different types of fish provide different kinds of nutrients, and different plants require more of some nutrients than others.
Even the kinds of microorganisms breaking waste down into fertilizer play a part in this complex system. At times, Brown said, it can become necessary to add additional nutrients to make up for deficiencies in the system. The acidity and salinity of the water can also be major factors.
Springworks has plants growing to maturity constantly, allowing Kenkel and his team to measure different qualities and environmental factors: the location in the greenhouse the plant grew in, the density of the leaves, and the effects of different temperatures, for example.
“It’s everything, anything you can really think of,” said Kenkel, who studied plant physiology at Bowdoin College.
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