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Abstract

A method of preparing a new granular homogeneous metal ammonium phosphate-alkylene urea buffered fertilizer, containing slow releasing water insoluble nitrogen of two types which provide sustained nitrogen release. The method is based on the discovery that a strong metal ammonium phosphate matrix may be formed to homogeneously contain fine particles of alkylene urea compounds. The new buffered fertilizer provides concentrated slow release nitrogens, and phosphate, and buffering amounts of metal nutrients. The alkylene urea may be formed in-situ from liquids concommittantly with the formation of the metal ammonium phosphates, or it may be admixed as finely divided alkylene urea solids. The preferred alkylene ureas are methylene ureas and polymers, isobutylene diurea, and crotonylidene diurea. The metal nutrients are divalent and are preferably magnesium, manganese, zinc, and iron reacted as oxides, hydroxides, or carbonates. The ammonium ion is supplied in the method as anhydrous ammonia, ammonium hydroxide, and preferably as ammonium phosphate. The phosphate is supplied as phosphoric acids, ammonium phosphate, or preferably as a combination of phosphoric acid and ammonium phosphate. The method is most effectively carried out in a high intensity mixer-reactor, comprising a cylindrical pan rotating around a near-vertical center containing a smaller diameter mixer rotating at a high rate of speed relative to that of the pan. The magnesium, ammonium, and phosphorous entities are reacted at about a mol ratio of 1.0 to 1.0 to 1.0 at about the boiling point of water, and at about atmospheric pressure to form a new fertilizer composition containing between 14 and 30 percent nitrogen with between 40 and 80 percent of the nitrogen insoluble in cold water and buffered to a pH between 6.0 and 8.0.

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