Sediment management in integrated aquaculture-agriculture systems: Sustainable use of fish culture sludge for organic fertilization of Terminalia arjuna.

Aquaculture systems generate large amounts of sludge that represent serious environmental threats if discharged directly into local ecosystems. However, this nutrient-rich sediment can contribute to nutrient cycling by being applied as an organic fertilizer to ornamental medicinal trees during their early growth stages. To investigate the potential advantages of using recirculating aquaculture system sludge (RASS) and biofloc technology sludge (BFTS) as organic fertilization alternatives to chemical fertilization, a pot trial was conducted at the Faculty of Agriculture, Cairo University, Egypt. The sludge effects on growth, NPK content, and high-performance liquid chromatography (HPLC) quantification of 24 phenolic phytocompounds of Terminalia arjuna seedlings were evaluated. Stimulation of growth and an increase in chemical composition were observed in seedlings supplied with BFTS + ½ NPK, followed by seedlings treated with BFTS, RASS + ½ NPK, RASS, and ½ NPK, as compared to unfertilized seedlings or seedlings supplied with NPK fertilization. Our results demonstrate that both sludge types are effective organic fertilizers for ornamental medicinal tree production and are comparable to or superior to commonly used synthetic fertilizers. The results also indicate that using RASS and BFTS can be considered an environmentally friendly method of organic waste management through nutrient recycling. Furthermore, we propose an integrated farm design for the recovery of both dissolved and solid nutrients that can be a sustainability paradigm in which zero-waste discharge, as well as environmental and economic benefits, can be achieved under the UN Sustainable Development Goals.