The Role of Organic Amendments and Marine-Biomass–Derived Resources in Enhancing the Physicochemical Properties of Horticultural Growing Media

Horticultural growing media such as cocopeat are widely used in soilless cultivation systems to support plant growth. While effective in providing physical support and aeration, these substrates are typically nutrient-deficient and chemically inert, necessitating regular supplementation through fertigation. This reliance on synthetic nutrient solutions presents challenges including nutrient leaching, limited water retention, and unstable pH, which may compromise the long-term sustainability of drip-irrigated systems. This book chapter explores the use of organic amendments specifically vermicompost and biochar and inorganic co-amendments, including rock phosphate and fly ash, to improve the physicochemical properties of horticultural media. In addition, it emphasizes the synergistic effects of coapplying fly ash, rock phosphate, and biochar with vermicompost. Biochar enhances pH buffering, cation exchange capacity, and nutrient retention, while fly ash supplies essential minerals, and rock phosphate promotes phosphorus availability, within the vermicompost matrix. The chapter also examines the potential agronomic application of marine-derived resources, including biochar produced from seaweed species, such as Laminaria pallida and Gracilariopsis funicularis. Marine resource-derived biochar offers promising nutrient composition (N, P, K, Ca, Mg, S) and structural benefits. In contrast, it may pose challenges such as high salinity, elevated pH, and the potential presence of heavy metals (e.g., Cd, Cr, Zn, Cu, and Fe). Coapplication strategies with other organic amendments, such as vermicompost, have been evaluated as potential approaches to mitigate these issues. In addition, innovations in green fertilizers synthesized from seawater using hydrogen-based clean energy technologies are discussed as emerging climate-smart alternatives to fossil fuel-based inputs. Drawing on recent empirical studies, this chapter synthesizes the current knowledge on amendment technologies and marine-based resources, identifies key research gaps, and proposes future directions for enhancing the sustainability and efficiency of horticultural growing media in modern soilless agriculture.