Use of Phosphogypsum in Brazilian Agriculture.

Phosphogypsum (PG; CaSO4.2H2O), a by-product of the production of phosphoric acid, is greatly available in Brazil. PG has many agronomic uses, with the most important in the country being as a subsoil acidity ameliorator. Ample agronomic field trials have shown that many crops developing in soils containing high amounts of aluminum (Al; > 0.5 cmolc dm-3) and/or low amounts of calcium (Ca; < 0.5 cmolc dm-3) in the subsoil (20 to 40 cm for grain crops and 40 to 60 cm for perennial crops) can significantly favor from adequate application of PG. It was proven that this product can favor root elongation due to a decrease in Al toxicity and/or increase of Ca in soil deeper layers, which results in higher crop production (more water and nutrients). Brazil has been utilizing PG with success since the mid 80’s. The amount of PG to be applied depends on subsoil chemical and particle size properties, with more of the product used as percent subsoil clay increases. It is to note that use of PG in Brazil generally does not pose problems in terms of detrimental presence of radioactive chemical elements once phosphoric acid in the country is produced from igneous phosphate rocks, which are generally low in such elements. Amounts of PG to be applied should be driven by proper soil analysis as not to over apply the product, which can lead to leaching of nutrients, most especially some micronutrients. In summary, data available shows that phosphogypsum can be used for soil amelioration in Brazil and, most likely other tropical soils, with success when taking into consideration the soil, the plant and the product.