Abstract
Phosphogypsum (PG), a calcium sulfate dihydrate by-product of wet-process phosphoric acid production, is generated globally at over 300 million tons per year, yet only 14% is currently reused or recycled, with the remainder stockpiled or discharged into coastal areas. Its agricultural use as a soil amendment has grown considerably, yet a rigorous, integrated synthesis of its agronomic benefits, environmental risks, and practical limitations has been lacking. This review addresses that gap through analyzing questions under what conditions, at what rates, and with what co-amendments can PG be applied safely and effectively to degraded agricultural soils? Literature was searched across PubMed, Scopus, Web of Science, and Google Scholar using Boolean keyword combinations centered on PG and soil properties, crop yield, radionuclides, heavy metals, soil microbiology, and circular economy themes, covering 2000 to 2025. The review demonstrates that PG improves soil aggregate stability, reduces bulk density, increases porosity and water permeability, and corrects sodicity and secondary salinization through Ca 2+ –Na + exchange in saline, sodic, and magnesium-affected soils. It reliably supplies calcium and sulfate–sulfur across vegetable, cereal, legume, and industrial crop systems, and alleviates subsoil aluminum toxicity in acid tropical soils where lime is ineffective. The novelty of this review lies in integrating agronomic performance, microbial community responses, and radionuclide and heavy metal risk into a single analytical framework, positioned within a circular economy context. Critical knowledge gaps identified include insufficient long-term multi-year field data, geographically restricted study populations, and the near-total absence of source-specific contaminant characterization as a prerequisite for agronomic use.