Aquaponics, an agricultural technique, relies on a symbiotic relationship between fish and plants to cultivate food.
The plants in the aquaponics system are fertilized by the water, and the scraps produced by the plants are cleaned and consumed by the fish.
The bacteria in an aquaponics system decompose fish waste into nitrates and phosphates, which are subsequently utilized by the plants for their growth.
Nutrients in fertilizer for plants
Plants require a total of 16 essential nutrients in order to thrive and develop. These nutrients can be obtained from both synthetic and organic plant fertilizers. While nitrogen, phosphorus, and potassium rank as the most crucial nutrients for plants, various other minerals are equally vital for ensuring robust growth.
Organic fertilizers like manure or compost possess all 16 essential plant nutrients, unlike synthetic fertilizers that usually possess only a few. Nevertheless, synthetic fertilizers are typically more concentrated than organic ones, hence they should be used with caution. Improper use of synthetic fertilizers can harm plants and contaminate the environment.
Organic fertilizers release nutrients gradually over time, making them more environmentally friendly compared to synthetic fertilizers. This gradual release prevents nutrient leaching, which has the potential to pollute groundwater supplies. Additionally, organic fertilizers enhance soil quality by increasing the content of organic matter.
Do aquaponics systems need fertilizer?
Aquaponics systems are growing in popularity as a gardening method, as they integrate fish farming with hydroponics and utilize fish wastewater, which is high in nitrogen, to fertilize plants.
Afterwards, the water is filtered by the plants prior to being returned to the fish tanks, resulting in a self-sustaining system that does not rely on any additional fertilizer.
Aquaponics systems, which have been utilized for centuries in China and other regions of Asia, have witnessed a surge in popularity in North America in recent years. This increased interest can be attributed to people’s desire to embrace sustainability and foster an eco-friendly environment.
Aquaponics is an ideal method for individuals with limited space or residing in urban areas, as it enables them to grow their own fresh vegetables and fish. In this system, the fish waste supplies all the necessary nutrients for the plants, which, in turn, serve as a natural filter, purifying the water for the fish.
The water is naturally filtered by the plants, thus cleaning it for the fish. The plants receive the necessary nutrients from fish waste, and in return, they assist in purifying the water for the fish.
Producing your own food can be achieved through an aquaponics system, which allows you to cultivate vegetables and fish simultaneously. In this system, the plants play a vital role in naturally filtering the water, thereby ensuring its cleanliness for the fish.
Setting up an aquaponics system is a straightforward way to begin organic gardening as it offers multiple benefits. The fish supply protein while the vegetables offer vitamins and minerals.
Afterwards, the water is sent back to the fish tank, restarting the cycle. This procedure not only purifies the water, but also ensures a consistent nourishment for the plants.
The initial step in converting fish waste into plant nutrients involves the bacteria existing in the aquaponics system. These bacteria decompose the fish waste into ammonia and nitrites. While ammonia is harmful to both fish and plants, nitrites are not. The bacteria then transform the ammonia into nitrates, which serve as nutrients for the plants.
The quantity of nitrates in the water is determined by the number and size of fish being cultivated in the system.
The success of the aquaponic system depends on how well the grower manages it. Aquaponic plants thrive in a soil-free environment and solely rely on nutrients produced by fish waste. Technically speaking, the growers do not use any fertilizers.
In the event of a nutrient deficiency, aquaponics practitioners may have to supplement the cycle with specially designed organic fertilizers meant for this particular planting technique in order to restore its balance.
Aquaponics is a system that recirculates and utilizes fish waste for plant growth in media beds. Tanks contain fish, shrimp, and other aquatic animals, whose waste is directed to trays within aquaponic systems for plant cultivation. The bacteria in the grow beds undergo the nitrogen cycle to convert the ammonia into nitrates, which serve as fertilizers for the plants.
Aquaponics is heavily dependent on nutrients, as plants require nitrogen (N) for the production of amino acids, proteins, enzymes, and chlorophyll. Nitrate and ammonium are the two commonly utilized nitrogen compounds for plant fertilization.
The roots promptly take up nitrates, which can be retained without causing harm, and these nitrates are highly mobile within plants. However, plants can only absorb ammonium in limited quantities due to its harmful effects, making it impossible to retain large amounts. If the concentration of nitrates exceeds 10 mg L-1, it hinders the plant’s ability to take in calcium and copper, encourages shoot growth over root growth, and imparts a vivid green color to the leaves.
Potassium (K) not only has important roles in photosynthesis, protein synthesis, enzyme activation, and cell division and extension, but it also functions as a transporter of other substances and carbohydrates through the cell membrane.
Maintaining the cell’s osmotic potential and controlling stomatal opening are crucial. Plants with a low potassium content are more susceptible to spore attacks, water stress, and sudden temperature drops. The growth of roots, the rapid development of buds, and the quantity of flowers are promoted by phosphorus (P).
P is readily taken in by plants and can accumulate without causing harm. The main purpose of P is to facilitate the production of ATP, which is crucial for plant metabolism. The quantities needed by plants are relatively small, accounting for only 10–15% of their N and K requirements. The presence of calcium (Ca) plays a vital role in controlling cell wall growth, membrane permeability, cell division, and cell elongation.
The increased availability of the plant increases its resistance to bacterial infections and fungi attacks. The relationship between water movement between roots and aerial portions and absorption is strong. This is because it moves through the xylem, and various factors such as low temperatures at the root level, lack of water (due to drought or a salty solution), or excessive relative humidity in the air all have an impact. Chlorophyll molecules are formed by utilizing the mineral magnesium (Mg).
When the pH levels decrease to below 5.5, it loses the ability to move and hinders the absorption of potassium (K) and calcium (Ca). The plant shows signs of sulfur deficiency as yellowing occurs between the veins of the leaves and the basal leaves show interior chlorosis. The plant requires sulfur (S) in quantities similar to phosphorus, and it is best absorbed when present in a ratio of 1 part sulfur to 10 parts nitrogen. Sulfur is absorbed by the plant in the form of sulfate.
Iron (Fe) is considered one of the most important micronutrients due to its crucial role in various biological functions, including photosynthesis. To ensure optimal absorption, the pH level of the solution should range between 5.5 and 6.0. It is also important to avoid excessive manganese (Mn) concentration, as it can lead to competition between the two elements. Despite plants containing high concentrations of chlorine (Cl) (0.2-2.0% dw), it has only recently been recognized as a micronutrient. Chlorine is rapidly absorbed by plants and exhibits a high level of mobility within them.
The control of stomata opening and the photosynthetic process is its main function. Deficiencies are not common, but one typical sign is leaves drying out, particularly at the edges. Plants are negatively affected by excessive sodium (Na) as it is toxic and inhibits the absorption of other ions. Manganese (Mn) plays a role in several coenzymes and is crucial for root cell growth and disease protection.
The availability of the nutrition solution is determined by the pH and competition with other nutrients. Boron (B) is necessary for fruit setting and seed development and it competes with calcium. The ideal pH range for the nutritional solution is below 6.0, with 4.5 to 5.5 being optimal. Deficit signs of boron deficiency can be observed in early, dark-green structures and young leaves with a leathery texture and increased thickness. Zinc (Zn) is an important component in certain enzymatic reactions.
The absorption of nutrients by the nutrient solution is significantly influenced by the pH and P supply. Zn absorption is promoted when the pH levels range from 5.5 to 6.5. The plant’s ability to absorb zinc is restricted by low temperature and high P levels. Copper (Cu) is necessary for both respiration and photosynthesis activities. However, its absorption is reduced at pH levels higher than 6.5, and pH levels lower than 5.5 can lead to dangerous consequences.
Molybdenum (Mo) is necessary for nitrogen metabolism and protein synthesis. It is more easily obtained at neutral pH levels than other micronutrients. The initial indications of deficiency are chlorosis and necrosis along the primary veins of older leaves, while the new leaves show deformities. Aquaponics relies on the system’s water and fish feed as the primary nutrient sources.
After any leftover feed decomposes in the tanks, fish consume a large part of the meal, which is either used for growth and energy or expelled as soluble and solid feces. The microbes in the system must break down the solid feces in order for the nutrients to be accessible to plants, while the plants can easily absorb the soluble excretions.
Limitations of using fertilizers in plants
The environment can suffer negative consequences from excessive use of fertilizers, as they can run off into waterways and lead to algal blooms.
The presence of these blooms can cause a decline in water quality and an increase in toxins, posing a threat to both humans and animals. Additionally, the excessive use of fertilizer can result in soil erosion, as well as pollution of air and water.
Fertilizers are necessary in order for plants to grow, yet there exist restrictions on the amount of fertilizer that can be utilized. The excessive usage of fertilizer can result in the pollution of water and harm to plants. Furthermore, surplus fertilizer can seep into the groundwater, leading to environmental issues.
If not used properly, nitrogen, phosphorus, and potassium, the essential nutrients for plant growth, can also become pollutants, which is why they are included in fertilizers.
Excess nitrogen in waterways can result in the formation of algae blooms, which can result in the depletion of fish populations. Algal blooms in lakes and rivers can be caused by phosphorus and can result in a reduction in water quality. Moreover, potassium has the potential to leach into groundwater and contaminate drinking water sources.
It is important to use fertilizers sparingly and only when necessary in order to decrease the possibility of water pollution.
Researchers add secret ingredient to improve plant growth through aquaponics
The microbiome is a collective term for the team of tiny microbes that are present on the roots of every healthy plant. These microbes are essential for plant health as they contribute to plant growth, produce hormones, reduce plant stress, supply nutrients, and protect against diseases.
In general, plants typically depend on the microbes present in the soil of their planting location. However, in hydroponic systems, which involve water-based plant growth, scientists such as Scott Lowman and Emily Zhou at the Institute for Advanced Learning and Research (IALR) can intentionally introduce beneficial bacteria to the roots of the plants.
These beneficial bacteria have a significant impact as they cause plants to grow larger and at a faster rate. Zhou can have nearly 1,500 plants growing simultaneously when the indoor greenhouse at IALR is operating at maximum capacity. The growth of these plants is closely observed, and the temperature, humidity, light exposure, and water pH are adjusted precisely for ideal growth. In the initial hydroponic plant experiments conducted in the IALR greenhouses, Zhou witnessed a growth increase of up to 60 percent compared to conventional soil planting techniques.
Lowman said that it is unheard of in the plant world.
Not only does aquaponic produce grow faster, but it also tends to have a longer shelf-life, which can be advantageous for growers and help in reducing food waste for consumers.
According to Zhou, if your hydroponic lettuce grows to be this large, it becomes appealing, especially considering its price of $3 or $4. Additionally, these lettuce can be stored in the refrigerator for a month or four weeks and will still remain fresh.
Lettuce and tilapia: an unlikely but effective duo
For thousands of years, plants have depended on the microbes in their roots. It is only in the last 20 years that researchers have started to discover the specific microbes and their functions within the microbial team. Due to the difficulty of culturing bacteria in the lab, the study of as much as 99 percent of bacteria on Earth has not been conducted.
In addition, the process of finding the appropriate mixture of microbes that benefit plants can be time-consuming and demanding, especially considering only a portion of bacteria can be cultivated. However, the team is currently introducing the microbiome obtained from fish aquaculture as a new natural source of advantageous bacteria.
The IALR is working together with aquaculture specialists at the Virginia Tech Seafood Agricultural Research and Extension Center (VSAREC) to research aquaponics, a merging of aquaculture and hydroponics. In this study, VSAREC supplies the water for the fish tanks, while IALR focuses on monitoring plant growth. Collaboratively, they will examine the microbial community responsible for the effectiveness of this integrated system.
Alongside the presence of microbes, the water found in fish tanks possesses an abundance of nitrogen, which aids in the fertilization of plants. Within an aquaponics system, the nutrients derived from the fish are exceptionally efficient as fertilizers due to the swifter delivery of nutrients to the plant roots through the water-based system in comparison to soil.
The fish benefit from the plants and the microbes in their roots as they remove ammonia from the water before it returns to the fish tanks. This compound, which is rich in nitrogen, aids in plant growth and prevents the accumulation of ammonia in fish tanks that can harm or cause the death of the fish.
VSAREC Director Michael Schwarz stated that the bacteria, which convert ammonia to nitrite and then nitrate in a sequential manner, serve as the core component of the system.
Healthy plants start with healthy water
The microbes that are important in aquaponic systems also present an additional safety concern. Unlike fish, which are usually cooked thoroughly to eliminate any bacteria, leafy greens such as lettuce, which are commonly grown in aquaponic systems, are consumed raw. At this time, there have been no instances of aquaponically-grown produce being recalled due to bacterial contamination, according to Food Safety Specialist Reza Ovissipour from VSAREC. The teams at VSAREC and IALR are focused on maintaining this record.
The main focus is on pathogenic bacteria as they can find hiding spots within the rough, textured lettuce leaves. These hiding spots enable the bacteria to form resilient groups called biofilms, which are more resistant to cleaning or eradicating compared to single cells.
Ovissipour is utilizing a new approach, known as nanobubbles, to treat the water and produce from aquaponic systems. These nanobubbles comprise ozone, a type of oxygen, which effectively ruptures bacterial cells resembling the action of bleach. However, unlike bleach or other chemical sanitizers, the nanobubbles are capable of purifying the water without harmfully affecting the plants thriving within the system.
AREC researchers have also created a sample food safety plan that can serve as a blueprint for actual aquaponics businesses to develop their own customized plans.
The plants grow fast — and businesses can, too
Aquaponics offers a wide range of combinations beyond the typical lettuce and tilapia examples. Numerous options exist for pairing ornamental fish, food fish, freshwater fish, and saltwater fish with various plants. However, the majority of systems prioritize leafy greens that thrive and mature rapidly within the aquaponic setup.
According to Jonathan van Senten, an Extension Specialist of VSAREC, he has collaborated with aquaponics businesses to assist in the creation of business plans, mainly focusing on aquaculture economics and marketing. He mentioned that the economic appeal of this industry lies in the ability to cultivate high-value crops more rapidly.
Van Senten said that they are aiming to make aquaponics a complete and ready-to-use operation.
