Engineered carbon-based fertilizers for sustainable agriculture: physicochemical mechanisms of nutrient release, soil health improvement, and plant uptake
Abstract
The intensive use of synthetic mineral fertilizers has sustained global crop productivity but has also contributed to greenhouse gas emissions, nutrient losses, and progressive soil degradation. Carbon-based fertilizers (CBFs) represent an emerging class of functional carbon materials that integrate nutrient retention and delivery with carbon stabilization and soil–rhizosphere interactions. CBFs can be derived from diverse biomass feedstocks, including crop residues, livestock manure, and organic waste, through thermochemical and biological conversion routes such as pyrolysis, hydrothermal carbonization, composting, and anaerobic digestion. This review critically examines the evolution of CBFs from conventional carbon-rich soil amendments toward engineered nutrient-delivery systems with tailored physicochemical and interfacial properties. Particular emphasis is placed on carbonization and activation strategies; pore architecture; specific surface area; surface charge; oxygen-containing functional groups; and surface functionalization, and on their influence on nutrient adsorption–desorption, ion exchange, complexation, diffusion, and controlled release. Advanced modification strategies, including chemical activation, co-pyrolysis, mineral–organic functionalization, and nano-carbon integration, are further evaluated, with emphasis on nano-biochar, graphene derivatives, and carbon dots. The review also examines interactions among carbon matrices, nutrients, and rhizosphere microorganisms, distinguishing established physicochemical and microbial mechanisms from emerging stimuli-responsive and nano-enabled delivery concepts. Finally, the laboratory-to-field translation gap is critically assessed, highlighting how soil heterogeneity, environmental variability, material transformation, and microbial dynamics influence CBF performance and identifying priorities for reproducible, field-validated, and environmentally responsible fertilizer development.