Purpose <p>This study examines gyttja’s impact on cotton growth, oxidative stress, and soil microbial activity under saline and non-saline conditions.</p> Methods <p>The experiments were conducted under saline (SS) and non-saline (NS) soil conditions. Fiona cotton variety was used as the plant material. The treatments included control (<b>non-application</b>), gd8 (8&#xa0;g), gd16 (16&#xa0;g), gd24 (24&#xa0;g), SS, SS + gd8, SS + gd16, and SS + gd24.</p> Results <p>Gyttja applications significantly improved plant growth and stress tolerance. In non-saline soil, gyttja enhanced root and shoot development, with the highest dose (gd24) increasing root length by 26.5% and shoot weight by 54.7%. In saline soil, it effectively mitigated salt stress, leading to a 62.1% increase in root length and a 142.3% increase in root weight. Additionally, the application reduced oxidative stress by lowering hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) levels while increasing proline accumulation. The gd24 treatment reduced H₂O₂ by 35% and MDA by 29% under saline conditions. Soil microbial activity was also significantly enhanced, with catalase increasing by 346% and urease by 38.2%, contributing to improved soil health and nutrient cycling. These findings suggest that gyttja is a promising organic amendment for improving plant resilience and productivity, particularly under saline conditions.</p> Conclusions <p>These results suggest that gyttja can be an effective soil amendment that supports plant health and improves soil quality.</p>