The invention discloses a
urea sulfate coated urea slow-release granular
fertilizer. The
urea sulfate coated urea slow-release granular
fertilizer is prepared through the following steps of: adding 100kg of
urea granules of which the diameters are 2-4.5mm to a rotary drum type
coating machine, preheating the urea granules to 40-45 DEG C, spraying 1-10kg of a binder namely
urea sulfate, uniformly mixing the preheated urea granules and the
urea sulfate so as to obtain a mixture, spraying 1-20kg of
metasilicate powder, cooling the mixture and the
metasilicate powder, spraying 1-10kg of mounting addition agents (a mixture of
solid paraffin and
liquid paraffin) of which the temperature is 50-60 DEG C, cooling the mixture, the
metasilicate powder and the mounting addition agents to a
room temperature, and repeating the
coating operation 2-3 times. The binder namely the
urea sulfate is prepared through the steps of slowly adding1-2kg of concentrated
sulfuric acid of 90-98wt% to every 1-10kg of urea and performing a reaction in a reaction tank. The urea
sulfate coated urea slow-release granular
fertilizer disclosed by the invention adopts a urea sulfate metasilicate slow-release film, tests prove that the urea sulfate metasilicate slow release film has a favorable slow-release effect, and in the slow-release process, the slow-release film is not liable to collapse and is easy to degrade. The urea sulfate has subacidity, so that the application range of the urea sulfate is wider than that of
sulfur coating urea. The urea sulfate coating film realizes double-film double-control effects, and has the advantages of high efficiency,
environmental protection, low cost and the like.