The application of fish wastewater to improve the plant growth, development and yield of lettuce (Lactuca sativa L.)

Demand for low-cost and affordable alternating sources of plant nutrient responses to boost the nutrient level of damaged arable farmlands has been a main concern for soil scientists, agronomists, and local farmers. The objective of this study is to investigate the effect of fish wastewater on the growth parameters, yield, and biomass productivity of lettuce (Lactuca sativa L.) as compared by using in aerated nutrient solution under deep water culture (DWC) technique. The experiment was carried out to investigate shoot and root fresh and dry weight, total leaf number, leaf chlorophyll content (SPAD), photosynthesis, leaf total chlorophyll (a+ b), leaf total carotenoid content, total leaf area, leaf NRA activity, total root length, root volume and average root diameter. Lettuce plants were examined by using an aerated deep-water culture (DWC) technique in a fully automated climate room for six weeks. The seedlings were transplanted onto 8 L continuously aerated pots containing mix of different ratios of fish effluent water with tap water with six different treatments (T1, T2, T3, T4, T5 and T6) and replicated three times. The fish wastewater effluents did not reduce the growth of lettuce plants. Shoot and root fresh and dry matter, total leaf number, leaf total chlorophyll (a+ b), leaf total carotenoid content, total leaf area, leaf NRA activity, total root length, root volume and average root diameter of lettuce plants were significantly increased with under T3 treatment (Tap water + 1.5 mM N + 50 ml Nutrient solution + 8 ml Fe + 1000 ml Fish effluent water). However, the lettuce plants grown under T4 treatment (Tap water + 1.5 mM N + 250 ml Fish effluent water) had the lowest shoot and root fresh matter, total leaf number, photosynthesis, total leaf area, leaf NRA activity, total root length, root volume and average root diameter. The compost derived from the fish wastewater plays an important role in supplying the nutrients for cultivating the lettuce plants. Also, in this study appreciable nutrients were significantly obtained in treatments treated with fish wastewater, as compared with the ground (tap) water. Thus, grown lettuce with aquaculture is a good source of nutrition for human consumption.