Microalgae hold significant potential as nature-based solutions in agriculture, offering benefits such as nitrogen fixation, enhanced nutrient cycling, stimulation of beneficial microbes, strengthening soil structure, and carbon sequestration. Yet, despite their potential, the role of microalgae, particularly through their interactions with soil systems, remains largely underexplored. Their ability to generate bioactive substances such as phytohormones, amino acids, and extracellular polymeric substances (EPS) fosters soil aggregation, nutrient availability, water retention, biological soil crust, and soil restoration, which ultimately supports plant growth and productivity. Moreover, the thermochemical conversion of microalgal biomass into biochar offers an effective strategy to improve carbon sequestration while simultaneously enriching soil nutrient content, thereby increasing crop productivity. While microalgae-based products often demonstrate strong efficacy under laboratory and greenhouse conditions, their performance in the field remains constrained by soil physicochemical properties, ecological incompatibility, competition with native microbial communities, and environmental variability, leading to inconsistent outcomes and highlighting the need for soil-specific, field-relevant strategies. Furthermore, the lack of standardized and cost-effective cultivation, formulation, and processing, along with low biomass yield and energy-intensive production, continues to limit their large-scale adoption in agricultural systems. Therefore, this narrative review aimed to discuss the mechanisms of coupling microalgal biomass and biochar to enhance soil health and crop growth, while also addressing field-performance constraints. It provides a balanced view of the potential and challenges of microalgae-based technologies for sustainable soil management and crop productivity. Overall, microalgae possess significant potential to improve soil health, increase crop yields, and contribute to sustainable agriculture that can withstand climate challenges.

Greenhouse gas emissions from agricultural crops remain a critical challenge for climate change mitigation. This review synthesizes evidence on cropland management interventions and global N2O mitigation potential. Agricultural practices such as cover cropping, agroforestry, reduced tillage, and diversification show promise in reducing CO2, CH4, and N2O emissions, yet uncertainties in measurement, verification, and socio-economic adoption persist. This review highlights that biochar application reduces N2O emissions by 16.2% (95% CI: 9.8–22.6%) in temperate systems, demonstrating greater consistency compared to no-till agriculture, which shows higher variability (11% reduction, 95% CI: −19% to +1%). Legume-based crop rotations reduce N2O emissions by up to 39% through improved nitrogen efficiency and increase soil organic carbon by up to 18%. However, reductions in synthetic fertilizer use (65% lower in legume vs. cereal systems) can be offset by the effects of biological nitrogen fixation. Optimized nitrogen fertilization, when combined with enhanced-efficiency fertilizers, can reduce N2O emissions by 55–64%. Complementing this, global-scale analysis underscores the dominant role of optimized nitrogen fertilization in curbing N2O emissions while sustaining yields. To bridge gaps between practice-level interventions and global emission dynamics, this paper introduces the ICEMF, a novel approach combining field-based management strategies with spatially explicit emission modeling. Realistic implementation currently achieves 25–35% of technical potential, but bundled interventions combining financial incentives, training, and institutional support can increase adoption to 40–60%, demonstrating ICEMF’s value through integrated, context-adapted approaches. Only peer-reviewed articles published in English between 1997 and 2025 were selected to ensure recent and reliable findings. This review highlights knowledge gaps, evaluates policy and technical trade-offs, and proposes ICEMF as a pathway toward scalable and adaptive mitigation strategies in agriculture.

Drought stress is one of the most severe abiotic constraints limiting wheat productivity worldwide, particularly during early developmental stages that determine crop establishment and yield potential. Sustainable, biologically based strategies that enhance drought tolerance without environmental cost are therefore urgently needed. In this study, we evaluated the individual and combined effects of chitosan (Cs), microalgae (Ma) (Nostoc linckia, MACC-612), and a chitosan–microalgae nanoparticle formulation (Cs-Ma) on germination performance, early seedling growth, and molecular stress responses in two wheat (Mehregan and MV Nádor) cultivars with contrasting drought sensitivity under polyethylene glycol (PEG)-induced osmotic stress (−2 and −4 MPa). Drought stress significantly reduced germination percentage, germination rate, and radicle and coleoptile development in both cultivars, especially at −4 MPa. Application of Cs and microalgae individually partially alleviated these negative effects; however, the combined Cs-Ma treatment consistently produced the strongest improvements in seedling vigor and biomass accumulation under both moderate and severe drought stress. Evaluation of drought tolerance using tolerance index (TOL), stress tolerance index (STI), and stress intensity (SI) demonstrated that Cs-Ma markedly increased STI and reduced SI across most germination traits, indicating enhanced drought tolerance and lower stress sensitivity, particularly in MV Nádor. These physiological responses were supported by transcriptional reprogramming in radicle tissues, including upregulation of genes involved in polyamine biosynthesis (TaSPDS, TaSAMDC), phenylpropanoid metabolism (TaPAL), and protein protection (TaHSP70), along with moderated induction of polyamine catabolism (TaPXPAO). Overall, the results reveal a synergistic interaction between chitosan nanoparticles and microalgae biomass, highlighting Cs-Ma as an effective, eco-friendly biostimulant for improving early-stage drought tolerance in wheat.