slow-acting nitrogen fertilizers in the form of a white powder with particles smaller than 0.5 mm. They have low hygroscopicity, do not cake, and scatter well, even with high humidity.
Methylene-urea fertilizers contain 37–40 percent nitrogen (4–12 percent of which is water-soluble). They are produced by condensation of concentrated aqueous solutions of urea and formaldehyde in an acid medium. The resultant product (mainly methylene urea) is filtered and pulverized. Methylene urea is poorly soluble in water, and consequently it does not wash out of the soil to a great extent. It gradually turns (to the extent of 60–70 percent) into ammonium and nitrate compounds, which are accessible to plants. This makes it possible to supply the plants with nitrogen for several years by applying methyleneurea fertilizers. Methylene-urea fertilizers are used in regions of excessive moisture and irrigated farming, and they are most efficient when used under highly intensive crops such as tea, citrus, or cotton.