Perfecting Soilless Farming

Agricultural conditions in the Kingdom of Saudi Arabia are remarkably difficult. With one of the lowest rainfall rates in the world, the desert country has no permanent rivers or lakes. In such an environment, natural resources must be used efficiently, and creative thinking becomes a necessity to ensure food security for the nation.

These environmental pressures are inspiring a team of researchers at KACST to develop pioneering approaches to farming that not only cater to the country’s difficult climate, but create superior produce. One key research area is aquaponics, the practice of farming plants and fish in a symbiotic environment where the presence of one directly promotes the growth of the other.

Yousef Alhafedh, professor of genetics and director of KACST’s Center of Excellence for Wildlife Research, has been leading teams of researchers to develop and refine their aquaponics system for more than a decade. The name of the technology is a portmanteau of ‘aquaculture’, the practice of fish rearing, and ‘hydroponics’, the growing of plants without the use of soil.

Simple, yet effective

The concept of aquaponics is as simple as it is effective: a sizeable tank houses a large, high-density population of fish. As the fish grow, the water that houses them is filtered using a gravity-fed technique to keep the water free of large particulate matter, such as dirt. The water is then pumped to long channels in which aquatic plants are grown. At the end of the channels, a small pump sends the water back to the fish tank.

During this cycle, waste matter from the fish provides nutrition for the plants, which in turn clean the water of toxins, such as total ammonia nitrogen (TAN), for the fish. These fish-farming toxins are also hazardous to the environment, and so cleaning the water in this way also has an environmental benefit when the water is eventually discharged to the sea.

One of the greatest benefits is efficiency: “One kilogram of lettuce cultivated in the soil will consume 400 liters of water. In comparison, our system will produce 8 kilograms of lettuce and 1 kilogram of fish with 300 liters of water,” says Alhafedh. In as little as three months, the fish tanks can produce 45 kilograms of fish per cubic meter. The system also retains the vast majority of the water it uses, requiring just minor refilling as water is lost to evaporation. As the majority of the water flow is mediated by gravity, the team’s aquaponics system uses much less energy. And, in comparison to traditional hydroponics systems, the plants in the aquaponics are nourished by the fish, cutting costs.

Saudi Vision 2030 — the country’s blueprint for future prosperity and a set of ambitious goals over the next 12 years — explicitly prioritizes aquaculture, and highlights the importance of preserving the kingdom’s water resources. Furthermore, in February 2018, the government of Saudi Arabia approved .5 billion of financial support to help the Ministry of Environment, Water and Agriculture meet 16 strategic targets in line with the Vision 2030 plan.

The team first revealed their research at the 2006 International Conference on Recirculating Aquaculture, when they described the design and operation of their aquaponics system over a period of five months, producing tilapia and seaweed for human consumption. Since then, the researchers have worked to maximize the produce output of their aquaponics technology. In 2012 and 2014, their research published in the journal Reviews in Agriculture detailed the successful trialing of different seaweeds, different planting densities, and different flow rates for the water.

Alhafedh’s team also received governmental support to set up an aquaponics system near the Red Sea for the purpose of shrimp farming, a highly competitive industry in Saudi Arabia. “This project was a success, and also produced large amounts of seaweed which can be utilized by humans or animals thanks to its high nutritional value.”

Food for farms

It wasn’t until 2017 that Alhafedh’s team shifted their attention to the animal feed industry, when researchers discovered a type of aquatic plant, duckweed, growing in the southwest of the country. Alhafedh explains that duckweed can grow in as little as 20 hours, and contains a protein content of 40 to 45 percent. “Nobody was growing duckweed using aquaponics,” says Alhafedh. “So, we tried to see if we could maximize its production using our technology.” The pilot study was a great success. Within one week, says Alhafedh, all of their hydroponics channels were filled with the plant.

Such a high yield of protein is highly attractive to Saudi Arabia’s farming industry, especially considering the versatility of duckweed. With its high nutritional value, the plant can be used to feed fish, cows, sheep, and camels. As it stands, Saudi Arabia currently imports the majority of its animal feed from other countries, says Alhafedh, and so efforts are warranted to become more self-sustaining. Due to the large camel population in the country, Saudi Arabia is the world’s number one consumer of barley, using 8 million tons per year. And its farming uses so much water, says Alhafedh, that the government is cracking down on its production in efforts to save the country’s resources. These restrictions highlight just how important water-saving farming techniques such as Alhafedh’s are for Saudi Arabia’s food security.

Now the team is looking to scale up their efforts. Housed in an enormous 5 square-kilometer greenhouse, their aquaponics system uses channels that are a meter wide and 33 meters long, and Alhafedh and his team are in the process of designing a large-scale aquaponics system with channels up to 300 meters in length. Alhafedh says that, for this, his team is currently surveying land in the southwest of Saudi Arabia, closer to where duckweed is naturally found and the climate is cooler and more suitable for its growth. The team hopes to start this next stage by 2019.

The researchers will also undertake work to create an animal feed formula, a major component of which will be aquaponics-produced duckweed, that can feed their fish as well as be sold to industry. 

Alongside aquaponics, Alhafedh oversees a number of projects under the ‘protected agriculture’ category, the concept of farming under engineered environments to maximize the agricultural output. Other technologies the team is working on include a greenwater system, which does away with the aquatic plants and instead utilizes algae and bacteria within fish tanks to maintain the quality of the water.

One of the biggest challenges the team faces in its research is transferring its technology from the lab to the land. Despite its efficiency, Alhafedh says that they must make the system and directions for its use as accessible as possible to farmers. As aquaponics deals with fish and plants in a carefully balanced ecosystem, the researchers must ensure that farmers are given adequate training to ensure that they can utilize their aquaponics technology to the best of its capacity.

In an aquaponics system, 98.5% of the water is recycled as only  1.5% needed per day to keep at the level.

1. Al-Hafedh, Y. & Alam, A. Recirculating aquaculture in Saudi Arabia: Aquaponics and greenwater. Proceedings of the 6th International Conference on Recirculating Aquaculture, 440– 447 (2006).

2. Al-Hafedh, Y. et al. Experiments on an integrated aquaculture system (seaweeds and marine fish) on the Red Sea coast of Saudi Arabia: efficiency comparison of two local seaweed species for nutrient biofiltration and production. Reviews in Aquaculture 4, 21–31 (2012).

3. Al-Hafedh, Y. et al. Bioremediation potential, growth and biomass yield of the green seaweed, Ulva lactuca in an integrated marine aquaculture system at the Red Sea coast of Saudi Arabia at different stocking densities and effluent flow rates. Reviews in Aquaculture 6, 1–11 (2014).