Application of bentonitic clays in suspension fertilizer formulations

Four Ca-bentonitic clays from Alabama were evaluated for use in diammonium phosphate (DAP) or urea ammonium nitrate (UAN) fertilizer suspensions. The viscosity and gel strength of suspensions prepared with different proportions of a Western bentonite clay and sodium-exchanged Alabama clays were measured as a function of clay content and dispersant concentration. The results obtained suggested that three of the Alabama Ca-bentonites would replace about 40% of the more expensive Western bentonite in UAN and DAP fertilizer suspensions. The performance of the Nu-modified clays, prepared according to the Tennessee Valley Authority soda ash method, was as good or even better than those observed for the Mg-, NaIMg- or K-modified clays. The TVA clay modification procedure appears to be reliable and cost effective.