**Background:** Global food insecurity affects approximately 828 million people (10.5% of the world population) as of 2021, with Africa bearing the highest burden (20.2% prevalence). Conventional agriculture relies heavily on synthetic fertilizers and pesticides, but up to 50% of applied nitrogen fertilizer is not utilized by crops and instead causes environmental damage. Cyanobacteria offer an environmentally friendly alternative due to their ability to fix atmospheric nitrogen, produce bioactive compounds, and remediate polluted soils without requiring arable land for cultivation.
**Methods:** This is a narrative review synthesizing published literature on cyanobacterial applications in agriculture. The authors discuss cyanobacterial growth systems (open ponds and closed photobioreactors), extraction methods, and the range of bioactive metabolites produced, including phytohormones (auxins, cytokinins, gibberellins), phenolic compounds, terpenoids, carotenoids, peptides, polysaccharides, and vitamins. The review covers studies on crop species including tomato, maize, chickpea, pea, broad bean, barley, wheat, radish, and pepper.
**Key Results:** Multiple studies demonstrate significant yield improvements: Anabaena laxa increased chickpea yield by 104% and nitrogen content by 50%; Anabaena laxa increased pea yield by up to 39% and protein content by 11%; Anabaena sp. and Nostoc sp. increased maize yields by 20–30%. Treatment of broad bean with Nostoc muscorum induced root length by 30%, shoot length by 44%, root fresh weight by 2-fold, shoot fresh weight by 1.5-fold, root dry weight by 67%, and shoot dry weight by 1.6-fold. Photosynthetic pigment, carbohydrate, and protein contents increased by 52%, 20%, and 1.7-fold respectively. Aphanothece sp. treatment in tomato increased root length by 112.65%, shoot length by 53.70%, and nitrogen, phosphorus, and potassium uptake by 185.17%, 119.36%, and 78.04% respectively. Arthrospira platensis polysaccharide extract amplified shoot dry weight by 1.4-fold in both tomato and pepper, with root weight increases of 2.30-fold in tomato and 67% in pepper. For abiotic stress mitigation: Oculatella lusitanica LEGE increased reduced glutathione by 66.67% and decreased H2O2 by 32.5%, MDA by 21.43%, and proline by 12.5% in salt-stressed lettuce. Arthrospira platensis treatment in faba bean under Fusillade herbicide stress decreased root proline by 42.9%, shoot proline by 33.3%, and MDA by 98.7%. Nostoc muscorum priming in barley under Granstar herbicide increased yield parameters: number of spikes/plant by 90%, spike length by 23.5%, spike weight by 1.13-fold, grains/spike by 82.4%, and 100-grain weight by 92.3%. For bioremediation, Nostoc muscorum and Anabaena subcylindrica removed Cu (12.5–81.8%), Co (11.8–33.7%), Pb (26.4–100%), and Mn (32.7–100%). Spirulina platensis removed Zn at 87%, 80%, and 70.5% at initial concentrations of 0.5, 1, and 2 mg/L respectively. Phormidium sp., Oscillatoria sp., and Chroococcus sp. removed 94% of diesel and 99% of total petroleum hydrocarbons.
**Clinical Implications:** Cyanobacteria represent a cost-effective, sustainable alternative to synthetic agrochemicals, costing approximately one-third the price of chemical fertilizers. Their application as biofertilizers, biostimulants, and bioremediation agents can reduce environmental pollution from agricultural runoff while maintaining or improving crop yields. The mechanistic basis involves production of phytohormones, induction of antioxidant enzymes (SOD, CAT, GPX, GST), upregulation of detoxification genes (GSTZ, GSTU, GSTL, TaGS, TaGPX), and enhancement of non-enzymatic antioxidants. Genetic transformation with cyanobacterial genes (e.g., HSP70 from Aphanothece halophytica, flavodoxins from Anabaena sp.) has shown promise for improving stress tolerance in crops. These findings support the integration of cyanobacteria into sustainable agricultural practices to address food security challenges.