A review of the long-term effects of organic amendments on soil fertility highlights their significant role in enhancing soil properties and sustainability. Organic amendments, such as compost, manure, and other organic residues, improve soil fertility by increasing organic matter, enhancing microbial activity, and improving soil structure. Long-term experiments (3–60 years) show that these amendments can increase soil organic carbon by up to 90% compared to unfertilized soil and up to 100% compared to chemical fertilizers. They also improve soil physical fertility by increasing aggregate stability and decreasing bulk density. Compost application enhances microbial biomass carbon and enzymatic activity, leading to better soil health and crop yields. Long-term compost applications can increase crop yields by up to 250% and improve soil quality without reducing crop yield. Organic amendments also contribute to climate change mitigation by sequestering carbon and reducing greenhouse gas emissions. While there is no evidence of negative impacts from heavy metals in compost, their long-term application can enhance soil organic nitrogen content, storing it for future use. The review emphasizes the importance of long-term trials to assess the slow-acting effects of organic amendments on soil fertility and crop production. Organic amendments are crucial for sustainable agriculture, helping to reduce reliance on chemical fertilizers and promoting nutrient cycling. The study concludes that organic amendments are effective in improving soil fertility, enhancing crop yields, and supporting sustainable agricultural practices.A review of the long-term effects of organic amendments on soil fertility highlights their significant role in enhancing soil properties and sustainability. Organic amendments, such as compost, manure, and other organic residues, improve soil fertility by increasing organic matter, enhancing microbial activity, and improving soil structure. Long-term experiments (3–60 years) show that these amendments can increase soil organic carbon by up to 90% compared to unfertilized soil and up to 100% compared to chemical fertilizers. They also improve soil physical fertility by increasing aggregate stability and decreasing bulk density. Compost application enhances microbial biomass carbon and enzymatic activity, leading to better soil health and crop yields. Long-term compost applications can increase crop yields by up to 250% and improve soil quality without reducing crop yield. Organic amendments also contribute to climate change mitigation by sequestering carbon and reducing greenhouse gas emissions. While there is no evidence of negative impacts from heavy metals in compost, their long-term application can enhance soil organic nitrogen content, storing it for future use. The review emphasizes the importance of long-term trials to assess the slow-acting effects of organic amendments on soil fertility and crop production. Organic amendments are crucial for sustainable agriculture, helping to reduce reliance on chemical fertilizers and promoting nutrient cycling. The study concludes that organic amendments are effective in improving soil fertility, enhancing crop yields, and supporting sustainable agricultural practices.