OMAN: Aquaponics: a promising method for growing fish and crops in Oman

Aquaponics is the combination of fish production (aquaculture) with the soil-less production of plants (hydroponics). It operates within a closed-loop system and utilises minimal resources. Fish feed provides most of the nutrients required for healthy plant growth. These nutrients, excreted directly by the fish, or generated by the microbial breakdown of organic wastes, are absorbed by growing plants. Nutrient removal by the plants in turn treats the water by removing nitrogenous compounds, such as dissolved ammonia, which are harmful to fish. Water is then re-oxygenated and returned to the fish tanks. Fresh, potable water is added to the system, as necessary to replace evaporative loss.

Aquaponics Research in Oman
The combined growing of fish and greenhouse crops has been tested successfully in Oman. In 2010 a report was published by a group of scientists from Sultan Qaboos University and the Ministry of Agriculture and Fisheries for the combined production of tomatoes and red hybrid tilapia. The trials were conducted at the Rumais Agricultural Station. This research is now being extended with support from the Agricultural and Fisheries Development Fund, which is operated by the Ministry of Agriculture and Fisheries.

New varieties of salad crops and various fish species will be grown in a climate-controlled greenhouse and the results will be made available to growers. The unit in Rumais will also function as a demonstration facility. The main research objectives are to examine the production and uptake of minerals and their effects on the growth of plant crops, fish and plant crop productivity, the potential costs/benefits for farmers and quality and safety issues.
Commercial Development
The commercial development of large-scale aquaponics is being pioneered in Oman by Water Farmers Canada in collaboration with the Al-Raid Business Corporation. Their initial project, developed on a site at Manuma, is now in its third phase of expansion and has the seen the production of commercial quantities of fruits, salads and vegetables in systems integrated with the production of tilapia.

Production systems
Two main systems are used in aquaponics. The first involves growing crops in shallow grow-beds, using media to provide support for root systems. Expanded clay balls are commonly used to provide the physical support necessary for the roots of tall or trellised plants. The system operates on a flood and ebb system, where each tank is filled with mineral-rich water and drained 2-3 times each hour. A second method, used for smaller plants such as herbs and salads, involves floating the plants in a styrofoam raft. The plants are grown in small coir pots and receive their necessary minerals from the fish tank via the water which circulates around their exposed roots beneath the floating rafts.
Aquaponic systems need to be run intensively for maximum benefit with carefully managed planting and harvesting cycles. This necessitates maintaining the necessary balance between the culture of fish and the growing of plants. This ensures adequate circulating minerals and maintenance of water quality. Whilst most benefits of aquaponics are normally derived from the sale of plants there is considerable interest in growing fish of high value.
Tilapia are hardy fish. They are able to survive high water temperatures and are a suitable species for aquaponics production in Oman. Other, more highly valued species, include the Asian sea-bass and koi carp, which are sold for aquaria and ornamental fish ponds.
Sustainability
The benefits of using soil-less culture techniques and water re-cycling provide considerable benefits for long-term sustainability. Water consumption is less than 10 per cent of normal levels for horticultural production and can be provided from potable supplies. This eliminates the risk of contamination with pathogens which may occur in ground-water supplies. Reduced water demand is clearly useful in a hot arid environment. There are no direct mineral or fertilizer costs since the primary mineral source is the fish feed, which is contributing also to fish production. Some small additions of alkaline salts, to maintain a stable, neutral pH and ferrous salts, to maintain the necessary iron content, are the only mineral additives used in aquaponics. The intensive nature of aquaponic production reduces the amount of land necessary for commercial production units. Additionally, aquaponic systems operate with a low energy footprint, by maximising the use of gravity for water flow.
Safety
Neither chemicals nor pesticides are used in aquaponic systems, which have a high level of environmental compatibility as they do not discharge effluents. Being the ideal closed loop system, all chemical and biological by-products of the system are naturally used and neutralised within the system itself. The systems can be initiated with potable water and there are no direct risks of contamination with coliform bacteria or salmonella, since these pathogens do not survive in cold-blooded animals, such as fish. As in all crop production systems cross-contamination is possible, but the risk is greatly reduced when compared with field crops or greenhouse production systems using soil. Major testing programmes on aquaponic produce in Canada and Hawaii have recommended normal washing procedures following harvest for raw salad crops and herbs. Farmers using aquaponic techniques also have opportunity to seek organic certification since no pesticides or chemicals are used during production and crops should remain free of any unwanted residues.
(Dr Stephen Goddard is the Director of the Centre for Marine Biotechnology at Sultan Qaboos University. All pictures were taken at the Al Raid Farm in Manuma, near Rumais).