Determination of mineral nutrient composition of fish tank effluent and its effect on growth and yield of bulb onion, Allium Cepa

Abstract

Fish tank effluent has been reported as a cheap bio-fertiliser, and increases soil physico-chemical properties, hence improving soil fertility thus high production of bulb onion. A study was conducted to determine mineral nutrient composition of fish tank effluent and its effect on growth and yield of bulb onion, Allium cepa L. at Kyambogo University. The study determined the physico-chemical properties of fish tank effluent at different concentrations, effect of fish tank effluent concentration on growth and yield of bulb onion and assessed the gross margin of bulb onions grown under different concentrations of fish tank effluent. Treatments included 0, 100, 200 and 400 ml/L, and were laid out in a Completely Randomized Block Design with six replications for two trials. Data was collected; on Electro conductivity (EC), Total Dissolved Solutes (TDS), Total Suspended Solids (TSS), Nitrogen (N), phosphorus (P) and potassium (K), growth, yield and gross margin. Data collected was analysed by One Way ANOVA for objective one and two using Genstat statistical package (15th edition). Gross margin was computed using excel 2017 version. All results on physico- chemical properties varied significantly (P < 0.05) among fish tank effluent concentration. Highest mean EC, TDS, and TSS were recorded in 400 ml/L being 559.00 ± 0.00/L μS/cm, 368.33 ± 0.33 mg/L, and 5033.33 ± 33.33 mg/L respectively, while the same treatment had the lowest pH (6.56 ± 0.30). Highest mean N, P and K (0.43 ± 0.09, 0.06 ± 0.01 and 0.08)% were recorded from 400ml/L while the lowest (0.02 ± 0.01, 0.01 ± 0.00 and 0.01)% from 0ml/L. At the final week (12WAT), effluent concentrations did not significantly (P > 0.05) affect mean leaf area as a key growth parameter. The highest mean yield (26.84 ± 0.69 t/ha) was from plots treated with 200 ml/L and the lowest (14.49 ± 1.22t/ha) from 0 ml/L. The highest gross margin (71.76%) was from 200ml/L while the lowest (64.26%) was from 0 ml/L. In conclusion, physico-chemical properties varied among the different concentrations. Fish tank effluent concentration did not significantly affect growth parameters, significantly affected bulb onion yield, bulb height and harvest index but none significant on bulb onion diameter. Fish tank effluent at a concentration of 400 ml/L is recommended as a bio-fertilizer, for having highest amounts of physico-chemical properties. Fish tank effluent at concentration of 200 ml/L is recommended for better bulb onion growth, yield and gross margin in bulb onion production. Further studies on comparison of tank fish effluent and other different types of aquaculture systems should be under taken in bulb onion production.