A process for preparing fertilizers

A process for preparing a fertilizer, releasing nitrogen slowly, containing ureaform and at least one other fertilizing substance, comprises:(a) reacting urea and formaldehyde in an aqueous phase at a temperature from 30° to 60°C, at molar ratios or urea/ formaldehyde from 1.2 to 2 and water/urea from 0.7 to 10, at a pH from 2 to 4, by addition of an acid substance;(b) mixing the thus obtained ureaform aqueous suspension with at least one other fertilizing substance and with a part of the recycled final product, which part is sufficient to ensure in the mixture a pH from 0.4 to 5.5, and granulating the mixture at a temperature from 50° to 85°C;(c) before the granulation ends, increasing the product pH to a value from 5.8 to 7 by addition of an alkaline substance; and(d) drying the product, and recycling a part thereof to the step (b).