Urea (urea-ammonium nitrate, or urea-ammonium mixture) is a combination of concentrated aqueous solutions of urea and ammonium nitrate, in which the mass fraction of urea is on average 31–37%, and ammonium nitrate is 40–48%. Three main brands of fertilizer are produced in industrial production: KAS-28, KAS-30 and KAS-32 with a total nitrogen content of 28, 30 and 32%, respectively. In some cases, the nitrogen concentration may be lower - at the level of 20–25%.
According to its physical properties, UAN is a transparent or light yellow liquid with a faint ammonia odor. The density of the solution ranges from 1.26–1.33 g/cm³, the reaction of the medium is neutral or slightly alkaline (pH 7–8). Stable physicochemical characteristics ensure the ability to store the fertilizer throughout the year.
The crystallization temperatures of different brands differ: for KAS-32 it is about 0 °C, for KAS-30 - about -9 °C, and for KAS-28 - up to -17 °C. Given this, in conditions of low temperatures it is more expedient to use KAS-28. The application is carried out with specialized units for liquid complex fertilizers, since KAS does not contain free ammonia. At the same time, surface application is less effective than incorporating the fertilizer into the soil.
UAN is used both for basic fertilization and for plant top dressing.
UAN solutions are not limited to the role of a simple nitrogen fertilizer. They are used to prepare multicomponent mixtures with trace elements, pesticides and growth regulators. This significantly expands the scope of UAN use in intensive crop cultivation technologies and allows you to reduce the cost of applying agrochemicals.
