Algae have emerged as versatile biostimulants and biofertilizers with significant potential to enhance crop productivity, nutrient-use efficiency, and tolerance to environmental stressors. This review synthesizes current knowledge on algal biodiversity relevant to agriculture, and their physiological, biochemical, and metabolic attributes and research gaps for sustainable agriculture. Reported applications demonstrate yield improvements typically ranging from 10-40%, enhanced nutrient-use efficiency, and partial replacement of synthetic fertilizers, including nitrogen-fixing 20-30 kg N ha⁻¹ season⁻¹ by cyanobacteria. Algal applications have also demonstrated effectiveness in mitigating abiotic stresses, including drought, salinity, heavy metal toxicity, and temperature, through improving antioxidant activities (30-80%), water-use efficiency, phytohormones, and stress response transcription factors, under both controlled and field conditions. In addition, algae-base nanoparticles (iron oxide, silica or ZnO, and silver) enhance plant productivity and stress mitigation, promoting both molecular and biochemical channels. This review integrates mechanistic insights with agronomic outcomes, and discusses practical considerations, including formulation strategies, delivery methods, cultivation systems, and scalability. Environmental performance such as reduced reliance on synthetic inputs and improved resource-use efficiency, are also highlighted. However, challenges related to production costs, regulatory uncertainties, compositional variability, and inconsistent field performance remain key barriers to large-scale adoption. Overall, algae-based technologies represent a promising pathway toward more sustainable and resilient agricultural systems. • Algae-based technologies enhance crop productivity and nutrient-use efficiency • Micro and macroalgae act as biofertilizers and biostimulants in sustainable farming • Algal metabolites regulate plant growth and abiotic stress tolerance mechanisms • Algae mitigate drought, salinity, and metal stress via molecular and physiological pathways • Environmental performance and scalability of algal technologies are critically evaluated
Imran et al. (Fri,) studied this question.