Abstract
PurposeAquaponics combine aquaculture with crop production in a mutual system. In this experiment, the growth of Amaranthus in aquaponics with tilapia fish was investigated.Methods500-liter water tanks containing tilapia fish at four initial stocking densities of 100, 150, 200, and 250 fish/m3 were used in triplicates, with a view to evaluate vegetable yields as influenced by fish biomass to water ratio. 1 g of Amaranthus seeds were sown in a 1 m2 planting trough, which contained gravel with a top layer of sandy soil. The pots were flooded with water from fish holdings by an aquarium pump.ResultsThe germination rate of Amaranthus was not significantly different across the experimental setup (P > 0.05). The growth rate of Amaranthus was significantly higher with increasing fish density (P < 0.05). The average lowest and highest of shoots dry biomass yield recorded were 0.36 and 1.95 g/plant at 8 weeks after of sowing, and this corresponds to fish stocking densities of 100 and 250 fish/m3, respectively. A high positive correlation was found between the shoot dry biomass of Amaranthus and fish stocking density. The survival of tilapia fingerlings was not significant different, while the production levels were 5.62, 4.77, 4.57, and 4.00 kg/m2 in 100, 150, 200, and 250 fish/m3.ConclusionsThe growth of Amaranthus in this experiment demonstrated that the plant could effectively utilize the nitrogenous waste from fish tanks for biomass production, even at a higher concentration, while considerations for moderate fish density are only for fish health.
Highlights
‘Aquaponics’ is the symbiotic assembly of plants and fish, where fish releases nitrogenous metabolic end products into the water, which are further metabolized by bacteria for the products to serve as nutrients for plants (Effendi et al 2015)
Aquaponics are appropriate in areas with limited land and/or water, because it produces more than three times the vegetables’ biomass, with greatly reduced water compared to traditional agricultural methods (Tyson et al 2011)
It was reported that aquaponic production of tilapia requires use of less than 1% of the water required in pond culture for equivalent yields (McMurtry et al 1990)
Summary
‘Aquaponics’ is the symbiotic assembly of plants and fish, where fish releases nitrogenous metabolic end products into the water, which are further metabolized by bacteria for the products to serve as nutrients for plants (Effendi et al 2015). Different growing parameters suitable for vegetables such as basil in an aquaponic system have been reported by Somerville et al (2014) and these include: pH (5.5–6.5), plant/m2 (8–40), and growing time (5–6 weeks) (Somerville et al 2014) While such information has been provided for some other vegetables such as: parsley, lettuce, cauliflower, broccoli, head cabbage, mangold, and cucumbers, Amaranthus has not been adopted this way. In this experiment, the growth of Amaranthus in a small-scale aquaponics system with tilapia fish was investigated with a view to evaluate both fish and vegetable yields and composite production as influenced by fish density. Detailed information on the environmental conditions essential for seed germination and the establishment of Amaranthus in different substrates is an important prerequisite for its adoption in an aquaponic environment
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