Effects of Rice Straw Biochar on Aquaponic Plant Growth, Nutrient Uptake and Bacterial Communities

By the 2030s, urban populations are anticipated to constitute 60% of the global population, necessitating sustainable agricultural methodologies to address associated challenges. Aquaponics, an innovative integration of aquaculture and hydroponics, emerges as a promising solution. Biochar, a carbon-rich material produced by the pyrolysis of organic matter, enhances soil ecological efficiency and may similarly benefit aquaponic systems. This study investigates the role of rice-straw derived biochar when incorporated into coco coir substrate in a deep-water culture (DWC) aquaponic system, examining its effects on plant growth, nutrient intake, and bacterial community dynamics using basil (Ocimum basilicum) and lettuce (Lactuca sativa). Results indicate that, while biochar did not significantly increase biomass, it did enhance the uptake of several key minerals. Optimal biochar concentrations were determined to be 40% for Mn, Fe, and Ca and 80% for S in basil and 80% for Mn, Zn, and Ca in lettuce. Microbial analysis revealed that the predominant bacterial phyla in the biochar-amended substrates were Proteobacteria, Bacteroidetes, and Firmicutes, which are essential for nitrogen cycling and plant growth enhancement. In biochar treatments exceeding 60% concentration, the nitrogen fixation functional group is predicted to play a more prominent role in basil and lettuce systems. These findings indicate the potential of biochar as an amendment for improving nutrient uptake and microbial activity in aquaponic substrates, offering a scalable approach to enhancing system productivity. By optimizing biochar applications, this study contributes to the broader goal of developing resilient urban food systems that can mitigate environmental impact while enhancing food security.