Nutrient Management in Aquaponics: Comparison of Three Approaches for Cultivating Lettuce, Mint and Mushroom Herb

TLDR

Aquaculture effluent alone often lacks sufficient nutrients for hydroponic plant growth, necessitating supplementation. The study aimed to determine the optimal supplementation level for lettuce, mint, and mushroom herb in aquaponic systems. Three aquaponic systems (A–C) and one hydroponic control (D) were set up with Nile tilapia, varying only in the addition of micronutrients, macronutrients, or an inorganic solution to assess supplementation effects. Lettuce produced the highest yield in system C, mint in system B, and mushroom herb in systems A and B; supplementation boosted lettuce growth but lowered its nutritional quality, whereas mint and mushroom herb thrived with minimal supplementation.

Abstract

Nutrients that are contained in aquaculture effluent may not supply sufficient levels of nutrients for proper plant development and growth in hydroponics; therefore, they need to be supplemented. To determine the required level of supplementation, three identical aquaponic systems (A, B, and C) and one hydroponic system (D) were stocked with lettuce, mint, and mushroom herbs. The aquaponic systems were stocked with Nile tilapia. System A only received nutrients derived from fish feed; system B received nutrients from fish feed as well as weekly supplements of micronutrients and Fe; system C received the same nutrients as B, with weekly supplements of the macronutrients, P and K; in system D, a hydroponic inorganic solution containing N, Ca, and the same nutrients as system C was added weekly. Lettuce achieved the highest yields in system C, mint in system B, and mushroom herb in systems A and B. The present study demonstrated that the nutritional requirements of the mint and mushroom herb make them suitable for aquaponic farming because they require low levels of supplement addition, and hence little management effort, resulting in minimal cost increases. While the addition of supplements accelerated the lettuce growth (Systems B, C), and even surpassed the growth in hydroponic (System C vs. D), the nutritional quality (polyphenols, nitrate content) was better without supplementation.