Agricultural Reuse of Phosphogypsum in Contrasting Soils: Wheat Yield, Potentially Toxic Element Uptake, and Soil Microbial Community Responses

Phosphogypsum (PG) is a high-volume industrial by-product that is receiving increasing attention as an alternative soil amendment. This study presents a two-year pot experiment evaluating the effects of PG on spring wheat (Triticum aestivum L.) grown on two contrasting soils: an acidic, sulfur-deficient Arenosol and a sodium-affected Solonetz. Treatments comprised an untreated control and PG applications at 2 and 10 t ha−1, applied once in year 1 and repeated at the same rates in year 2. In the Solonetz, PG increased grain yield by 48–73% in year 2 and 31–40% in year 1, with the lower dose (2 t ha−1) providing sufficient agronomic benefits. In contrast, no yield response was observed in the Arenosol. In both soils, PG acted as a slow-release sulfur source, increasing straw sulfur concentrations in the second year. Even the repeated application of the highest PG dose (10 t ha−1) did not increase Al, Cd, Cr, or Sr accumulation in wheat grain, indicating no treatment-related increase in trace-element accumulation. PG also increased soil microbial biomass and altered the microbial community structure in the Solonetz, including higher relative abundances of arbuscular mycorrhizal fungi and actinomycetes. Overall, these results demonstrate the dual agronomic function of PG in improving sodic soil productivity and supplying sulfur to nutrient-deficient sandy soils without increasing treatment-related trace-element accumulation, thus highlighting its potential as a soil amendment in sustainable nutrient management systems.