PHOSPHOGYPSUM IN AGRICULTURE - A REVIEW

Phosphogypsum is the term used for the gypsum by-product of wet-acid production of phosphoric acid from rock phosphate. It is essentially hydrated CaSO4, with small proportions of P, F, Si, Fe, Al, several minor elements, heavy metals, and radionuclides as impurities. Phosphogypsum appears to be good source of S and Ca for crops. Most of the studies showed that surface-applied gypsum or phosphogypsum ameliorated subsoil Al toxicity, acidity, and infertility in shorter time periods than did surface-applied lime materials. Phosphogypsum may prove to be superior to mined gypsum as an ameliorant for subsoil A1 toxicity, acidity, and infertility and as a conditioner for sodic soils, hardsetting clay soils, and subsoil hardpans because of its much higher rate of dissolution compared to that of mined gypsum. Gypsum and phosphogypsum, where they are readily accessible, are potential bulk carriers for micronutrients and low-analysis fertilizers. Increasing environmental demands to prevent contamination of ground water with nitrates and to minimize applied N and P losses in runoff, losses that promote rapid eutrophication of surface waters, may require the use of low-analysis fertilizers in commercial agriculture, at more frequent application, as they are now commonly used in recreational and residential lawns and gardens. Radionuclides, heavy metal impurities, and other pollutants at concentrations found in phosphogypsum do not appear to constitute environmental hazards to surficial ground water, soil, crop tissue, and the ambient atmosphere at rates normally used in agriculture. © 1993, Academic Press Inc.