Integrated Aqua-Vegeculture System

iAVs Schematic Diagram

The Integrated Aqua-Vegeculture System (iAVs),also informally known as Sandponics, is a food production method that combines aquaculture and horticulture (olericulture). It was developed in the 1980s by Dr. Mark McMurtry and colleagues at North Carolina State University including Professor Doug Sanders, Paul V. Nelson and Dr. Merle Jensen. This system is one of the earliest instances of a closed-loop aquaponic system.

Many of the modern developments and discoveries of aquaponics are generally attributed to the New Alchemy Institute and North Carolina State University. Further research on aquaponics at North Carolina State University was discontinued due to the fact that the system was ready for commercial application. Today's flood-and-drain systems, as favoured by backyard practitioners, are derived from this model.

Before the Integrated AquaVegeculture System, other systems that combined fish and vegetable farming used special tanks called clarifiers to remove solid waste from the water before it was given to the plants. While this process cleaned the water, it also took away important nutrients that plants need to grow well. As a result, these systems often had to add extra supplements to make up for the missing nutrients. iAVs is different because it uses sand to filter the water, which keeps the essential nutrients in the system. This means the plants get all the natural nutrients they need without needing extra supplements.

Tomato transplants in a biofilter (composed of sand, bacteria and plants) shown being irrigated with aquacultural water for the first time.

One benefit is the production of high quality food products in close proximity to center of need, and reduction of operating costs.

In an iAVs, fish are raised in tanks, and their nutrient-rich water irrigates and fertilizes sand-based grow beds that support plant growth, act as biofilters, and deliver nutrients. As plants and micro-flora absorb these nutrients, they purify the water, which is recirculated back to the fish tanks.

The system often includes an aeration device, such as an aerating cascade, to oxygenate the water before it returns to the fish tanks. This multi-functional use of sand beds contributes to the relative simplicity of the iAVs design compared to other aquaponic systems.

IAVS is also informally referred to as 'Sandponics' which is actually a trademark for Agricultural cultivating equipment that is unlike IAVS.

History

Development and Early Research

Dr. Mark McMurtry, along with Professor Doug Sanders, Paul V. Nelson, and Merle Jensen, pioneered the iAVs at North Carolina State University. The system was designed to address issues such as soil infertility, pollution, and water scarcity, which Dr. McMurtry observed during his time in Africa. The initial research aimed to create a sustainable and efficient method for producing nutrient-rich food while conserving water.

View of the research greenhouse approximately one week after transplant of tomato crop. The tanks are below the wood-grate walkway

IAVS Research Group

The Integrated AquaVegeculture System (iAVs) was developed through the collaborative efforts of several key researchers and experts in various disciplines. The principal investigator, Dr. Mark R. McMurtry, played a pivotal role in the system's inception and development. Dr. McMurtry, who holds a PhD in Horticultural Science and Integrated Bio-production Systems, focused on addressing issues like soil infertility, pollution, and water scarcity through the innovative use of sand as a filtration medium.

Several co-investigators contributed significantly to the iAVs project:

• Dr. Edward A. Estes, an expert in Agricultural and Aquacultural Economics, provided insights into the economic viability and sustainability of the system.
• Dr. Blanche C. Haning specialized in Integrated Pest Management and Plant Pathology, ensuring the health and productivity of the plants within the system.
• Dr. Ronald G. Hodson brought expertise in Aquatic Ecosystems, Fisheries Management, and Genetics, which was crucial for the aquaculture component of iAVs.
• Dr. Paul V. Nelson, a Fellow of the American Society for Horticultural Science (FASHS), focused on Botanical Mineral Nutrition and Greenhouse Management, optimizing plant growth conditions.
• Dr. Robert P. Patterson, a Fellow of the Crop Science Society of America (FCSSA), contributed his knowledge in Agronomy, Soil Fertility, and Plant Physiology.
• Dr. Douglas C. Sanders, also a FASHS Fellow, provided expertise in Horticultural Science and Plant Physiology.

Additionally, several principal consultants offered their specialized knowledge to enhance the system:

• Dr. J. Lawrence Apple in International Development and Plant Pathology.
• Dr. Marc A. Buchanan in Agricultural Ecology and Soil Science.
• Dr. Stanley W. Buol in Geomorphology, Mineralogy, and Soil Genesis.
• Dr. JoAnn Burkholder, a Fellow of the American Association for the Advancement of Science (FAAAS), in Phycology and Aquatic Ecology.
• Dr. James E. Easley in Aquacultural Economics and Business.
• Dr. Donald Huisingh in Ecology and Environmental Resource Recovery.
• Dr. Merle H. Jensen in Agricultural Program Development at the University of Arizona's Environmental Research Laboratory (UAZ ERL).
• Dr. Thomas Losordo in Recirculatory Aquaculture.
• Dr. L. George Wilson, a FASHS Fellow, in Horticultural Science and Extension.

Commercial Application and Modern Developments

Further research on aquaponics at North Carolina State University was discontinued once the system was deemed ready for commercial application.

Open Source

Dr. McMurtry is the Inventor of Record of iAVs, and made it open source in 1985.

Global Outreach

Following the completion of his PhD, Dr. McMurtry assumed the position of Research Associate with the International Programs at North Carolina State University. Between 1989 and 1994, he undertook extensive travel across sub-Saharan Africa and the Middle East, collaborating with local universities, international aid organizations, and agricultural professionals to showcase the advantages of integrated agricultural practices.

Modification and Commercialization

Following the completion of his PhD dissertation at North Carolina State University in December 1989, Mark R. McMurtry embarked on a series of trips to demonstrate the benefits of the Integrated Aqua-Vegeculture System (iAVs) to faculty, students, and aquaculture industry professionals. One notable event was a 3-day interactive workshop at the Meadowcreek Project in Fox, Arkansas, attended by Tom and Paula Speraneo.

In the early 1990s, Tom and Paula Speraneo, owners of S & S AquaFarm in Missouri, adapted the iAVs design by replacing sand with gravel and using above-ground tanks for fish. This modified system, known as "Speraneo Systems," employed bell siphons to facilitate an ebb-and-flow irrigation cycle, popularizing what is commonly termed flood and drain aquaponics.In 2005, Joel Malcolm purchased the Speraneo’s information kit and adapted it for use in Australia. The Australian Broadcasting Corporation's Gardening TV program featured Malcolm's home-based system, leading to a renewed interest in the basic flood and drain system.

The introduction of gravel in aquaponics brought about several significant changes. It reduced mechanical filtration capability, decreased populations and activity of soil organisms, and lowered aeration in the media bacteria and plant root zone. Additionally, it diminished nutrient utilization and system stability, leading to reduced fish survival, feed rate, and growth. These changes also resulted in increased capital costs with lower fish and plant yields, as well as higher operating costs per unit of production.

Operation

Operating an Integrated Aqua-Vegeculture System (iAVs) requires managerial skills developed through experience. The system is user-friendly and resilient to changes in water chemistry, allowing for minor errors. Prior experience in gardening or husbandry is advantageous.

First-time operators should receive minimal training in aquaculture management, pest prevention, and water quality monitoring. While experienced operators may make occasional errors, regular monitoring facilitates correction.

The startup phase is the most sensitive for balancing the iAVs, but once stabilized, the system becomes easier to maintain at optimal production levels.

Throughout the day, a portion of the water from the fish tank, along with the accumulated residues from the tank's bottom, is either scooped or pumped onto the surface of the filter and plant bed. This nutrient-rich water percolates through the sand of the filter bed, where larger waste particles are filtered out at the surface. Meanwhile, smaller particles and dissolved nutrients are absorbed by the roots of the plants and by the various microorganisms present in the filter bed.

This filtration and irrigation process occurs at regular intervals during daylight hours, potentially as many as eight times each day. The primary operational objective is to ensure that the total volume of the fish tank is incrementally and cumulatively circulated through the filter bed at least once each day.

Once an iAVs is established, the primary inputs required are fingerlings, seeds or transplants, fish feed, and an energy source to facilitate water movement.

Aeration

The fish tank and filter bed are positioned vertically to ensure adequate elevation change between the drainage outlet of the filter bed and the water surface level in the fish tank, facilitating the installation of a cascade aerator.

The cascade, consisting of a series of small waterfalls, is intentionally designed to disperse the water flow into smaller droplets, promoting efficient mixing of air (oxygen) with the water as it descends back into the tank by gravity.

Intermittent Irrigation

Irrigation water is pumped from the bottom of the fish tanks eight times daily and delivered to the biofilter (growbed) surfaces, with no irrigation at night. The water floods the biofilter surfaces, percolates through the medium, and drains back to the fish tank. The tank water level drops approximately 25 cm during each irrigation event. Therefore, the returning water provided additional aeration resulting from the effect of the cascade.

Energy usage

IAVs only requires 2 hours of water pumping per day and is suitable for off grid applications.

pH stabilization

In traditional recirculatory aquaculture, carbonate inputs are typically used to neutralize the acidification caused by nitrification. However, research has shown that alkaline amendments are unnecessary when the nitrogen input rate closely matches the nitrogen assimilation rates of plants. In the Integrated AquaVegeculture System (iAVs) research, water pH remained stable at approximately 6.0 when fish feed rates were balanced with plant nitrogen assimilation rates, avoiding excessive feed inputs.

The plant availability of both ammonium and nitrate ions helps to buffer the pH of the nutrient solution.

To see if plants help keep the water pH stable in the iAVs system, an experiment was done. For 42 days, they continued watering the system and feeding the fish, but no plants were grown in the biofilters. This was to check if plants were helping to keep the water pH stable. Without the plants, the water pH quickly dropped below 4.0.

Nutrients

Plant growth in the Integrated Aqua-Vegeculture System (iAVs) is sustained despite minimal nutrient levels in the recirculating water and the absence of supplemental fertilization, due to the system's constant replenishment characteristics.

Tomato crop after 4 weeks of growth in the biofilter. Flowering has started.

System Components

The Integrated Aquaculture System (iAVs) consists of a sealed containment structure designed to house the fish and to prevent the leakage of water, along with a sand filter bed designated for the growth of vegetable crops, and a water distribution system.

The three live components are plants, fish and bacteria.

Fish tanks

Fish are raised in tanks, producing nutrient-rich water.

Sand-based grow beds

These beds serve multiple functions:

• Plant support
• Biofiltration
• Particulate removal
• Nutrient delivery to plants

Water circulation device

Fish tank water and sediment are regularly removed and applied to the plant bed. The tank has a sloped base for easy waste extraction using a bucket or calabash. Enhanced circulation is possible with mechanical pumps powered by human or animal effort, or electric pumps with automated timers.

Tomato vines after 18 weeks (note: all fruit has been harvested)

Sand Composition

The sand used in the Integrated Aqua-Vegeculture System (iAVs) is critical to avoiding clogging and ensuring efficient filtration and rapid drainage. The ideal sand composition is 99.25% quartz sand, 0.75% clay, and 0.0% silt.

The criteria for selecting sand involved evaluating its water retention capacity through percolation tests, assessing its turbidity, and examining its drainage capabilities. The sand must be free of carbonates, heavy metals, and salts, and it should be inert.

The primary functional requirement for sand in a sand bio-filter is that the entire filter or plant bed must drain completely and efficiently. This requirement is crucial to prevent over-saturation of plants. Therefore, the sand should have a relatively coarse texture with minimal fines content, specifically no particles smaller than 200 microns in diameter.

The optimal filter sand should have a consistency similar to that of common table salt or granulated sugar, without any powdery constituents. Larger particles can be screened out if necessary. Generally, it is relatively straightforward to source an appropriate grade of sand.

Live Components

Plants

A broad array of vegetable crops may be cultivated in various combinations, which include tomatoes, cucumbers, melons, eggplants, peppers, beans, lettuce, assorted greens, and herbs; additionally, tree seedlings for reforestation projects may also be included.

Algae

Before the establishment and rapid growth of vegetable crops, the filter surface frequently becomes completely covered in algae.

Together, the bacteria and algae (collectively referred to as micro-flora) play a crucial role in the chemical transformation of fish waste products into nutrients that are available for plant uptake. During the initial start-up phase, they also serve as a nutrient sink or buffer until the vegetable plants reach growth rates that allow them to effectively purify the water themselves. As the plants grow larger, they increasingly absorb a greater percentage of the available nutrients from the water and begin to shade the surface of the plant bed.

This shading effect leads to a noticeable decline in algal populations, which subsequently releases the accumulated nutrients for absorption by the vegetable crops.

In the iAVs research, tilapia ate the algae that grew in the water and on the sides of the tank.

Horticultural subsystem

The upper surface of the plant/filter bed is prepared to a level grade and designed to accommodate the specific vegetable crops or species to be cultivated. Irrigation furrows are created between the rows of plants to promote the uniform distribution of irrigation water across the surface and through the volume of the filter bed. The plants are grown in raised sections of the sand which ensures the crown of the plants are kept dry.

In the Integrated Aqua Vegeculture System (iAVs), plants are grown in a horticulture subsystem where their roots are embedded in sand. This sand acts as a filtration medium, allowing the plants to absorb the nutrient-rich effluent water from the aquaculture subsystem. The plants effectively filter out ammonia and its metabolites, which are toxic to the aquatic animals. After the water has passed through the horticulture subsystem, it is cleaned and oxygenated, making it suitable to return to the aquaculture vessels. It uses a method of intermittent irrigation, flooding the furrows of the beds every 2 hours, during the day, until the sand is saturated. There is no irrigation at night,

Comparison with other systems

Previous integrated fish-vegetable systems removed suspended solids from the water by sedimentation in clarifiers prior to plant application.. Removal of the solid wastes resulted in insufficient residual nutrients for good plant growth; acceptable fruit yields had previously only been achieved with substantial supplementation of plant nutrients.

In contrast, iAVs extracts fish effluent, including solids, from the bottom of the fish tanks at regular intervals, up to eight times daily, from dawn to sunset.. The effluent is pumped directly from the bottom of the fish tank onto the surface of the sand bed, which serve as both biological and mechanical filtration and the locus for oxidation of organic solids.

DWC

In a comparative trial with Deep Water Culture (DWC), the economic feasibility analysis indicated that the Integrated Aqua-Vegeculture System (iAVs) produced more crops with a wider variety at almost 20% less capital expenditure and operational expenditure costs. Sand beds are able to grow a greater variety of plants than the DWC system.

In Deep Water Culture (DWC) systems, iron supplementation is typically required. In contrast, the Integrated AquaVegeculture System (iAVs) exhibits a significant increase in iron levels within the system and the crops without the need for external supplementation. This characteristic is considered one of the primary advantages of iAVs, as it eliminates the necessity for additional nutrient supplements.

Innovations in Filtration

IAVS does not need any mechanical filters as the filtration is performed by the sand.

In earlier aquaponic systems, the media often became clogged or resulted in uneven fertigation, which hindered their efficiency and effectiveness. The development of the reciprocating biofilter, where filter beds are alternately flooded and drained, has significantly mitigated issues such as clogging, channelization, and low oxygen levels. This innovation has enabled the retention of solids as a nutrient resource for plant growth, enhancing the overall productivity of the system.

Nutrient Availability

In other aquaponic systems, nutrients can become unavailable for plant uptake due to non-optimal system water pH.

In North Carolina, research by McMurtry et al. (1993) demonstrated that wastewater from recirculating aquaculture systems used for tilapia can effectively irrigate greenhouse tomatoes. The study found that the concentrations of essential nutrients such as nitrogen, phosphorus, potassium, and magnesium in the tomato tissues were adequate, indicating that fish wastewater can supply the necessary nutrients for tomato cultivation.

Fish production can be effectively achieved without the need for exchanging large quantities of water or utilizing complex biofiltration devices. The solid waste produced by the fish is retained in sand beds, facilitating good crop growth without the necessity for supplemental fertilizers.

Terminology

The Integrated Aqua-Vegeculture System (iAVs), developed by Dr. Mark McMurtry prior to the popularization of the term "aquaponics," represents a specialized methodology within the broader domain of aquaponics.

Hydroponics is traditionally understood as a soil-less cultivation method utilizing nutrient solutions, which can create confusion when discussing systems like iAVs that incorporate soil. This distinction emphasizes the unique methodology of iAVs as compared to other aquaponic systems, which generally do not utilize sand.

The ongoing dialogues surrounding the definitions of aquaponics and hydroponics highlight the necessity for standardized terminology in this field. Without clear definitions, the scientific advancement of aquaponics, including iAVs, may be impeded, as researchers and practitioners might struggle to communicate their findings and innovations effectively.

Additionally, this semantic challenge can influence public perception and the adoption of these systems, leading to potential confusion regarding the functionalities and requirements of various aquaponic setups. Establishing standardized terminology for describing aquaponic systems, including iAVs, will facilitate clearer communication, promote scientific progress, and enhance public understanding and support for these agricultural technologies.

External links

• IAVS Official Website