OPTIMIZING THE PLANTING DENSITY OF LETTUCE (Lactuca sativa) WITH TILAPIA (Oreochromis niloticus) IN A RECIRCULATION AQUAPONIC SYSTEM
An experiment was conducted for a period of 60 days to optimize the planting density of Lettuce (Lactuca sativa) with Tilapia in a shallow water recirculation aquaponic system. Four different planting density/m 2 i.e. 15 plants/m 2 , 20 plants/m 2 , 25 plants/m 2 and 30 plants/m 2 of hydroponic trough was used as four different treatments whereas, the stocking density of Tilapia (Oreochromis niloticus) was 100 fish/m 3 for all the treatments. Fish was reared in 300 L size tank and fed up to satiation twice a day with commercially available floating pellet with 30% protein level. The size of each of the hydroponic trough was 30 L which were made up with GI steel sheet. Styrofoam was used to cover up the hydroponic trough and made necessary number of hole according to the planting density of different treatment to support the plants in water medium. During the experimental period different water quality parameters were monitored regularly. Growth and yield of Lettuce were measured by means of number of leafs, plant height (cm), leaf area (cm 2 ), dry matter (g) and wet yield (kg/m 2 ). Whereas, Tilapiaâ€™s growth performances were evaluated on the basis of weight gain (g), production (kg/m 3 ), specific growth rate (% per day) and feed conversion ratio. At the end of the experiment, it was observed that Lettuce production were highest in T 3 (25 plants/m 2 ), although the growth performance was significantly better in T 1 and T 2 because of higher nutrient availability in these hydroponic trough. Fish production was significantly higher in T 3 and T 4 compared to T 1 and T 2 , although, highest production were observed in T 4 . Regarding both Lettuce and Tilapia production with suitable water quality parameters, it was therefore, optimized that, 25 plants/m 2 area of hydroponic trough was ideal to support 100 Tilapia/m 3 in a shallow water based recirculation aquaponic system.