This study investigates the potential of waste activated sludge (WAS) as a sustainable and cost-effective soil amendment for agricultural use. Through field trials, glasshouse experiments, and laboratory analyses, the research evaluates the effects of WAS on soil properties, plant growth, nutrient dynamics, and heavy metal content, comparing its performance with other organic amendments such as vermicast, chicken litter, and SustaiN™, a commercial fertilizer. The findings reveal that WAS application significantly enhances plant growth and yield. It also improves soil fertility by increasing organic matter content and promoting root development, though its high mineralization and nitrification rates necessitate careful management to minimize nitrogen losses. Heavy metal analysis indicates that while WAS contains elevated levels of metals like chromium and lead, these remain within permissible limits and do not significantly impact plant uptake. Cost analysis highlights WAS as the most economical option at $120/ha/yr, compared to significantly higher costs for other amendments. However, the study identifies gaps in understanding odour management, long-term environmental impacts, and the effects of WAS on livestock health, which warrant further investigation. In conclusion, WAS demonstrates strong potential as a viable alternative to traditional fertilizers, offering a balance between cost-effectiveness, nutrient availability, and environmental sustainability. Future research should focus on long-term field trials, expanded crop studies, advanced nitrogen monitoring, and economic feasibility to optimize its use in diverse agricultural systems. This study contributes to the growing body of knowledge on sustainable soil amendments, providing valuable insights for farmers, policymakers, and researchers aiming to enhance agricultural productivity while minimizing environmental risks.