Getahun, Abebe(Professor)Tadesse, Abebe2018-07-192023-11-092018-07-192023-11-092017-03http://etd.aau.edu.et/handle/123456789/9490This study was conducted at Addis Ababa University aquaponics research facility to determine level of Niger seed cake inclusion and mineral supplementation on aquaponics diet to improve Tilapia-Lettuce productivity in aquaponics system. Three main studies were conducted to determine the efficient level of Niger seed inclusion for tilapia (Oreochromis niloticus L.) growth, effective Niger seed dietary level on lettuce (Lactuca sativa L.) growth and effective mineral supplementation level for tilapia and lettuce growth. Mineral supplementation level was studied by taking the best Niger seed cake inclusion level for tilapia and lettuce growth. Five levels of Niger seed cake (NC) inclusions with different level of fish meal (FM) (NC:FM); 0 (Negative control diet; D1), 0.29 (D2), 0.83 (D3), 2.14 (D4), 3.4 (D5) and Hydroponics system(H) (Control 2; Positive control for nutrients) were tested against tilapia and lettuce growth and water quality attributes for 28 days. After decision on the best Niger seed cake inclusion level five mineral supplementation levels 0% (D1), 1.2% (D2), 2.3% (D3), 3.5% (D4) and 4.6% (D5) on fish diet were tested against aquaponics productivity taking the best diet from previous experiment as negative control. Impact of Niger seed cake inclusion level brought significant variation (p < 0.05) on water quality parameters but remain within the range suitable for growth and development of lettuce. Most tilapia and lettuce growth performance measures were significantly quadratic with NC:FM ratio in fish diet (r2 > 0.25, p<0.1). Highest Specific growth rate (SGR), Relative growth rate (RGR), Protein productive value (PPV), Crude protein content, Mineral retention (K, Ca, Fe and N) and feed efficiency response of tilapia were measured from D4. Similarly highest lettuce; Yield, Fresh biomass per plant, Leaf fresh weight, Root fresh weight from experimental diets were recorded from D4 that is statistically not different with H treatment (p > 0.05). Increased NC:FM composition resulted in quadratic decrease of Dry matter (DM) and mineral content. Mineral iv retained in lettuce was significantly correlated (p < 0.05) with diet mineral composition and resulted in increased mineral level recovered by lettuce and in water. Fish tank water mineral content response was also significantly quadratic with NC:FM ratios (r2 > 0.25, p < 0.1). Mineral supplementation performance on tilapia and lettuce growth was found to be significantly comparable among treatments and numerically lowest and highest RGR, and Protein efficiency ratio (PER) were achieved from treatment D1 and D5, respectively. Increased mineral supplementation level on fish diet brought significantly linear RGR, FCR, PPV and PER response (r2 > 0.5, p < 0.05). Among experimental diets significantly highest Absolute growth rate, Relative growth rate, Leaf weight ratio and lettuce yield were achieved from 2.3% mineral supplementation level (p < 0.05). Hydroponics mineral supplemented diet with a level of 2.3% resulted in significantly highest (p < 0.05) total (tilapia and lettuce) biomass yield and suitable growing environment for tilapia and lettuce. Aquaponics productivity can be improved through hydroponics mineral inclusion in fish diet which contains 2.14 NC:FM ratio supplemented with 2.3% hydroponics mineralenAquaponics ProductivityResponse for Niger Seed CakeThesis