Growth and Yield Performance of Lactuca sativa L. Grown in Hydroponics using Fish Effluents and Inorganic Fertilizer

Aquaponics is an emerging sustainable food production technique where waste from fish culture is used as a source of nutrients for crops grown in hydroponics system. The present study was conducted at the Agriculture Research and Development Center, Sita Eliya, Nuwara Eliya, Sri Lanka during November 2015 to January 2016, to compare the yield of lettuce (Lactuca sativa L.) grown in hydroponics using fish effluents and inorganic fertilizer. The experiment was laid in a Completely Randomized Design with 5 treatments and 4 replicates. The different nutrient solutions used as the treatments of this experiment were water (T1), Albert’s solution (T2), Catla waste water (T3), Common Carp waste water (T4) and Tilapia waste water (T5). Each nutrient solution was tested for its nutrient composition, temperature, pH and electrical conductivity throughout the experimental period. The plant growth and yield parameters measured were plant height (cm), number of leaves, canopy diameter (cm), root length (cm), fresh weight of plant, leaves and roots (g), dry weight of leaves and roots (g) and, yield (ton/ha). The fish related parameters measured were body weight (g), initial and final stocking density (g/m3) and the mortality percentage. The results showed that T2 stood out (p<0.05) with the highest plant height (12.27cm), canopy diameter (14.80cm), number of leaves (12) and root length (15.04cm), exhibiting a vigorous growth compared to the other treatments. A remarkable yield and shoot and root weight (fresh and dry) were also shown by T2 over the other treatments. Fish waste water in T3, T4 and T5 did not fulfill the nutrient requirement of lettuce due to the limited nutrients; nitrogen, phosphorus and potassium) produced by fingerlings. Therefore, these fish waste solutions need to be improved by increasing the feed quality and selecting fish within a suitable age range in order to obtain a yield comparable to T2, which is the commercially available Albert’s solution.