Abstract: A method for manufacturing a urea-formaldehyde slow-release nitrogen fertilizer includes steps of: mixing and heating urea and formaldehyde solution with a predetermined molar ratio of urea to formaldehyde; adjusting a PH value of hydroxymethylation reaction of urea and formaldehyde solution to 7.5-10.5; heating the hydroxymethylation reaction of urea and formaldehyde solution to the initial reaction temperature of 50° C.; adding a catalyst to start the hydroxymethylation reaction of urea and formaldehyde solution, and conducting hydroxymethylation reaction intermittently or continuously; heating cold urea-formaldehyde solution using the reaction heat of hydroxymethylation; adjusting the pH value of the methylenation reaction of urea and formaldehyde solution to 3.5-5.

Abstract: In one aspect, a multi-layered fertilizer includes a layer-by-layer coated fertilizer layer and a coating layer, wherein the fertilizer layer is separated from the coating layer, and one of the fertilizer layers is a fertilizer core; the fertilizer layer contains at least one of nitrogen fertilizer, phosphate fertilizer and potassium fertilizer, the coating layer is polyurea formaldehyde, which includes at least a polyurea formaldehyde having two to five carbon atoms. It can better control the release of nitrogen, phosphorus, potassium, calcium, magnesium and zinc in the fertilizer to meet the different nutrient requirements of different crops at different growth stages. The fertilizer can be prepared by a reactor, a slurry tank, a powdering tank and supporting facilities, which can control the amount of each layer of fertilizer and its position in the entire fertilizer granules according to a design procedure.