Urea

Urea is synthesised by reacting ammonia with carbon dioxide under heat and pressure, then formed into granules or prills for handling and spreading. Its guaranteed analysis is typically expressed as 46-0-0, reflecting its status as a straight nitrogen source with no phosphorus or potassium content.

Chemical formula

CO(NH₂)₂

Nitrogen content

About 46% total nitrogen, in amide form

Physical form

White, hygroscopic granules or prills

Solubility

Highly soluble in water

Urea supplies nitrogen only, initially in amide form. Soil urease enzymes hydrolyse it to ammonium, which soil microorganisms then oxidise to nitrate through nitrification, the same plant-available forms supplied by other nitrogen fertilizers.

• Contains no phosphorus, potassium, or secondary or micronutrients
• Nitrogen becomes plant-available after hydrolysis and, subsequently, nitrification
• Commonly blended with phosphate and potash materials to build compound products

Urea is used across cereal, oilseed, and vegetable production systems worldwide because its high nitrogen analysis reduces the cost of transporting, storing, and handling nitrogen relative to lower-analysis sources. It can be applied broadcast, banded, or dissolved into a liquid solution.

• High nitrogen density lowers transport and handling cost per unit of nitrogen
• Suitable for broadcast, band placement, fertigation, or foliar use in dilute solution
• A common base material for producing compound and blended fertilizers

Because surface-applied urea is vulnerable to ammonia volatilisation, incorporation into the soil, banding below the surface, or application ahead of rainfall or irrigation are general practices used to reduce nitrogen loss. Urease inhibitors are also used in some products and regions to slow the hydrolysis reaction.

Ammonia volatilisation is the principal loss pathway specific to urea, and it is greatest on warm, moist, alkaline or calcareous soils when urea is left on the surface without timely rainfall or irrigation. Once converted to nitrate, urea-derived nitrogen is subject to the same leaching and denitrification losses as other nitrogen fertilizers.