Effects of plant density and stem pruning on plant biomass yield and economic benefits in a low-cost gravel bed aquaponic system

ABSTRACT The combined yields of Oreochromis mossambicus and fruit crops – tomato, sweet pepper, and cucumber were investigated in a low-cost designed gravel bed aquaponic system to maximize overall yield. This study was modeled according to bioeconomic principles, which analyzed the experimental setup’s system design and management, biological characteristics, and economic performance. The study was conducted from March 2018 to February 2019. The growth performance of fish was determined using growth rate parameters, length–weight relationship, and condition factor. The effect of plant density and plant stem pruning was used to determine plant yield. Tomato, sweet pepper, and cucumber were subjected to two plant densities (5 and 8 plants.m2). Tomato and cucumber plants were pruned to one and two stems, while sweet pepper plants were pruned into two and three stems. A complete randomized design in triplicate was used. The FCR of 1.25; 97.5% survival rate; specific growth rate of 1.64%, LWR r2 of 0.945, regression coefficient b of 3.1 and condition factor K of 1.93 were recorded for the fish performance. Total yield, marketable yield, unmarketable yield, fruit mass, and number fruits.m2 were recorded. Tomato and cucumber plants pruned into two stems produced significantly (p < .05) higher total and marketable yields than plants pruned to one stem. Sweet pepper plants pruned into three stems produced significantly (p < .05) higher total and marketable yields than those pruned into two stems. A plant density of 8 plants.m2 produced a higher (p < .05) total and marketable yield of tomatoes, sweet peppers, and cucumbers than 5 plants.m2. Biomass yield in aquaponics can be optimized for higher economic viability by manipulating environmental conditions, adopting strategic culture management practices, and targeting higher market prices through scheduled production.