Integrated Aqua-Vegeculture System

The Integrated Aqua-Vegeculture System (iAVs) is a food production method that combines aquaculture and horticulture (olericulture) within a closed system. 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 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.

Benefits of integrating aquaculture and vegetable horticulture (olericulture) are: 1) conservation of water resources and plant nutrients, 2) intensive production of fish protein and 3) reduced operating costs relative to either system in isolation. This system is applicable to the needs and requirements of arid or semi-arid regions where fish and fresh vegetables are in high demand. Another 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 the nutrient-rich water from these tanks is used to irrigate and fertilize grow beds filled with plants that take up the nutrients, purifying the water, which is then recirculated back to the fish tanks. The system uses sand-based grow beds to perform multiple functions, including plant support, biofiltration, particulate removal, and nutrient delivery to plants, without the need for separate biofilters. 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.

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.

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.

System Components
The primary components of an iAVs include the fish tank, water distribution system, and the plant growing area which doubles as a sand biofilter. 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
Either a pump or manual method is required to circulate the water.

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 sand should be free from carbonates, heavy metals, and salts. The sand should be inert.

Horticultural subsystem
In the Integrated AquaVegeculture 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,

The sand is shaped into furrows and ridges. Surface irrigation, or furrow irrigation, is used to evenly distribute water throughout the grow beds. The plants are grown in raised sections of the sand which ensures the crown of the plants are kept dry.

Operation
The five main inputs to the system are water, oxygen, light, feed given to the aquatic animals, and electricity (or alternative or manual energy) to pump and oxygenate the water.

Intermittent Irrigation
Irrigation water is pumped from the bottom of the fish tanks eight times daily and delivered to the biofilter (growbed) surfaces. 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.

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.

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.