Comparative Study on Growth of Leafy Vegetables Reared in the Different Culture Systems between Coupled Aquaponics and Decoupled Aquaponics

Abstract

Aquaponics is a complex cultivation system that combines aquaculture and hydroponic cultivation in agriculture. Many of today’s coupled aquaponic systems (CAS) circulate water and nutrients from fish to plants to fish, but it is not always guaranteed that the fish preferences are completely aligned with the optimum requirements of the plants. The aim of decoupled aquaponic system (DAS) which would better secure optimal environmental conditions for both the plant and fish production units is to improve sustainability and productivity concomitant with lowering environmental emissions. The study examined the growth difference of leafy vegetables and Nile tilapia cultured in the culture systems between the CAS and DAS for 14 weeks. Five cultivars of European lettuces, including volare lettuce (Lactuca sativa. L. ‘Volare’), skilton lettuce (Lactuca sativa. L. ‘Skilton’), ovired lettuce (Lactuca sativa. L. ‘Ovired’), caipira lettuce (Lactuca sativa. L. ‘Caipira’) and ezabel lettuce (Lactuca sativa. L. ‘Ezabel’) were employed in the experiment period from 10th to 14th weeks. After planting leafy vegetables in the two systems, leafy vegetable productivity was compared at the end of growth period (32 days). The Nile tilapia (Oreochromis niloticus) used in the experiment was 125 kg with a average fish weight of 24 g, divided by equal weight into CAS and DAS. Feed supply was limited to 1.0% per fish body weight and supplied twice a day, and the amount of feed supplied to the DAS experimental group was increased by about 20% compared to CAS. In the leafy vegetable production comparison, there was no significant difference in the leafy weight of the four cultivars (P0.05) excluding the ovired lettuce cultivar (P0.05) between the DAS and the CAS experimental group. In weight gain (%) of fish, the DAS experimental group was effective in increasing fish weight due to the higher feed supply in fish tank of DAS. Therefore, this experiment showed that the DAS production method can provide optimal growth conditions for both fish and leafy vegetables.