Phosphogypsum Application in Coffee Fields and its Impact on Carbon Sequestration & Storage

Agricultural soils can effectively contribute to reduce the concentration of CO₂ in the atmosphere. Phosphogypsum (PG), a by-product of the phosphate fertilizer industry, primarily composed of calcium sulfate dihydrate (CaSO₄·2H₂O), has emerged as a potential soil amendment to improve soil health and enhance carbon sequestration. The objective of the study was to evaluate the effect of PG on soil carbon dynamics, nutrient availability, and fertility in a coffee plantation at the Cerrado in Minas Gerais, Brazil.

Phosphogypsum was applied at three rates 0, 7, and 56 Mg/ha—only to the coffee row shortly after planting. The PG, characterized by its fine particle size and high solubility, was evenly broadcast over the soil surface without incorporation. Soil samples were collected from both the coffee row and interrow , as well as from adjacent native vegetation with no PG application.

The application of PG influenced soil carbon stocks notably. In untreated coffee fields (0 Mg/ha), carbon stocks were measured at 260 Mg/ha in the row and 293 Mg/ha in the interrow. With the application of 7 Mg/ha PG, carbon stocks increased to 273 Mg/ha in the row and 312 Mg/ha in the interrow. At the highest application rate of 56 Mg/ha, carbon stocks further increased to 285 Mg/ha in the row and 333 Mg/ha in the interrow.​

Beyond carbon content, PG application improved nutrient availability, notably increasing concentrations of calcium and sulfur in the soil. Microspectroscopy analyses identified various functional groups of carbon, including aliphatic, aromatic, carboxylic, and polysaccharide compounds. A significant positive correlation (R² = 0.544, p < 0.05) was observed specifically between clay content and aliphatic C–H groups in soils treated with the highest PG rate (56 Mg/ha), suggesting enhanced stabilization of organic matter through mineral-organic interactions.

These findings indicate that phosphogypsum application can significantly enhance soil carbon sequestration and nutrient availability in coffee plantations. Implementing PG as a soil amendment aligns with Sustainable Development Goals (SDGs) related to climate action, life on land, and sustainable agriculture, offering a viable strategy for sustainable soil management in tropical agricultural systems.