This technology transfer project began in 2017 with a first pilot plant and the project was expanded in 2020 to a larger one. As explained by the Torre Pacheco Agricultural Demonstration Center (CDTA), “aquaponics consists of combining fish farming with plant cultivation in hydroponic systems, taking advantage of the synergies of both to achieve resource optimization and marketing of the two products, limiting and using the waste”. Thus, this innovative technique is presented as an alternative to the current activity and that has sustainability and respect for the environment as a priority, as well as the reduction of irrigation water and fertilizers.
As explained by those responsible, “the aim is to publicize this system, newly implemented in the Region of Murcia, for its possible use in farms, demonstrating that it is possible to achieve better use of water and reduce the use of fertilizers, managing to minimize the leaching of nitrates and obtain two products available for commercialization: fish (Tilapia) and vegetables».
The project shows how in aquaculture «the secretions of farmed animals can accumulate in the water, increasing its toxicity, making it necessary to renew the water; On the contrary, in an aquaponics system, the water flows through a closed circuit, the waste generated by the fish and the organic matter are separated from the water and used as compost and the ammonia is broken down into nitrites and later into nitrates by nitrifying bacteria.
These nitrates are used by plants as nutrients, so it is possible for the water to return to the fish tank without toxic products and thus start the process again. The surface on which the project is developed is 280 m2 between the two floors installed inside a polycarbonate greenhouse.
Three different hydroponic cultivation systems have been tested in order to see which one is best suited to each type of crop. The hydroponic system with deep water (Deep Water Culture), the hydroponic system with substrate and drip irrigation (Drip System) and the NFT (Nutrient Film Technique). Tilapia (‘Orochromis spp’) was used as a fish species due to its ease of rearing and rapid growth at high densities.
“The tilapias are fed with feed and a portion of duckweed produced in the center itself, derived from the recirculation of hydroponic crop drainage, in order to minimize inputs. The fish breeding facility initially consists of incubators where tilapia fingerlings are kept until 40/45 days after birth. Subsequently, they are transferred to a set of methacrylate tanks, designed for the production of fish between 45 and 70 days of life, to which a decanter tank, a biofilter, an aeration tank and an accumulator tank are added.
During the pilot tests, the settling tanks require daily maintenance, with siphoning to extract feces from the tank and screens. Likewise, add the volume of water necessary for losses in cleaning, absorption by the crop and evaporation. The remains of faeces extracted in the siphoning and settling meshes from the cleaning are used in landscaped areas for reuse, providing irrigation and fertilizer.
The species cultivated in the different systems and plants behave appropriately to the nutrition received, noting their development when the absorbent hairs of the roots are surrounded by the remains of feces. The different cultivation systems serve to adapt to each of them the appropriate species for its root development. At the end of the process, tilapias with a commercial weight of 400-500 g are obtained with six months of life, separating those that will be used for consumption from those that will be used as breeders.
Regarding the production of plants, it continues to be confirmed that more quality is obtained in species without the heart, green leaf lettuce, red lettuce, little gem, lollos, oak leaf, even trocadero lettuce than in iceberg lettuce and especially in the production of leaf small or baby leaf.
«Among the main advantages of implementing this system is the reduction of water and fertilizers and the consequent reduction of costs, the reduction of air, water and soil pollution, the reduction of space in relation to traditional crops or even as an attraction for agrotourism, explain those responsible for the project». These would be the main conclusions of the experience developed in these years by the promoters of the project, who consider that aquaponics is suitable for small agricultural producers with a view to taking advantage of local markets and agrotourism, as well as being environmentally sustainable.
To reduce production costs, especially in feed and energy, easy-to-produce and low-cost products that reduce the amount of feed, such as duckweed, and use photovoltaic energy to produce electricity should be used as a supplement to the feed. necessary for pumping and heating.
The results and information obtained will allow knowing those varieties that have a better performance and adaptation to the conditions of our Region and will be made available to farmers, technicians and anyone interested on the Training and Technology Transfer Service website www.sftt.es .
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