Ammonium-sulfate-coated urea nitrogen fertilizer, ammonium-sulfate-coated urea sustained-controlled release fertilizer and their preparation and application

The invention belongs to the technical field of fertilizer and particularly relates to ammonium-sulfate-coated urea nitrogen fertilizer, ammonium-sulfate-coated urea sustained-controlled release fertilizer and their preparation and application. The ammonium-sulfate-coated urea nitrogen fertilizer uses urea as a core that is coated with an ammonium sulfate layer, an ammonium sulfate/paraffin mixture layer or an ammonium sulfate/sulfur mixture layer, wherein when the core is coated with the ammonium sulfate layer, the mass ratio of urea to ammonium sulfate is (75-85):(15-25); when the core is coated with the ammonium sulfate/paraffin mixture layer, the mass ratio of urea, ammonium sulfate and paraffin is (75-85):(15-25):10; when the core is coated with the ammonium sulfate/sulfur mixture layer, the mass ratio of urea, ammonium sulfate and sulfur is (75-85):(15-25):10. The ammonium-sulfate-coated urea nitrogen fertilizer helps effectively reduce the concentration of ammonium ions in soil,significantly inhibit am