Keywords: Partially acidulated phosphate rock, Fertilizers, Crop response, Pollution, Manufacture, Tribology, Thermotribology.

Most fertilizers provide phosphorus in a water soluble form. Production of such fertilizers is costly in terms of energy and acid consumption and produces large quantities of waste gases and gypsum as by-products. Moreover many sources of phosphate rock are unsuited to the manufacture of water soluble P forms. Partial acidulation offers an alternative, cleaner, low cost technology and a range of methods are discussed. A wide range of agronomic assessments indicate that partially acidulated phosphate rock fertilizers are often as good as water soluble forms in supplying crop nutrient needs.

Yontcho Pelovski, Higher Institute of Chemical Technology, Sofia, Bulgaria.
M Kerry Garrett, The Queen's University of Belfast and Department of Agriculture for Northern Ireland, Belfast, UK.

27 pages, 8 figures, 1 table, 78 refs.