UTILIZATION OF PHOSPHATE ROCK IN TROPICAL SOILS OF LATIN AMERICA

The direct use of phosphate rock (PR) or some of its low-input altered products would seem to present a logical approach to overcoming this constraint. This paper selectively reviews the literature on soils and phosphorus fertilizer problems in tropical Latin America, identifies objectives for further research, and outlines a research program to meet those objectives. After a brief introduction, the literature review is presented. The review is divided into the following categories: (1) general P and soils review; (2) direct application of PR to soils; (3) characterizing phosphate rocks; (4) greenhouse and field investigations with PR; (5) greenhouse and field investigations with partially acidulated PR; and (6) greenhouse and field investigations with thermally altered PR. Next, the objectives of the research proposal are spelled out. First, an evaluation of the effectiveness of sources and methods of application of P fertilizers on soils of tropical Latin America is needed. Second, the research should determine the forms and availability of the reaction products of these fertilizers in soils as related to their initial and residual effectiveness. Finally, criteria need to be established for applying the results of the first two objectives to different soils and crops at various locations by conductng field experiments on selected soils throughout tropical Latin America. It is proposed that these objectives be accomplished through interrelated and pertinent laboratory, incubation, greenhouse, and field experiments. Currently, it is planned that the research will be carried out in Colombia, Brazil, Peru, Ecuador and other countries as may be appropriate over a 7-10 year period. The final part of the paper presents the reasoning and justification for the proposed research. Various charts and graphs and a 51-item bibliography (1943-1977) of English, Spanish, and Portuguese language references are also included.