Urea ammonium nitrate (UAN)

UAN is blended by dissolving urea and ammonium nitrate in water to a target nitrogen concentration, most commonly 28%, 30%, or 32% nitrogen. Because it is a solution rather than a solid, it is measured and applied by volume and is compatible with a range of liquid application equipment.

Composition

Urea and ammonium nitrate dissolved in water

Nitrogen forms

Approximately half amide (urea), with the remainder as ammonium and nitrate

Salt-out temperature

Higher-analysis grades crystallise at higher temperatures and are less suited to cold conditions

Physical form

Clear liquid, handled and applied by volume

UAN supplies nitrogen only, but across three forms that follow different pathways in soil. The nitrate fraction is immediately plant-available and mobile, the ammonium fraction is held on exchange sites before nitrifying, and the urea fraction is hydrolysed to ammonium before also nitrifying.

• Nitrate nitrogen is immediately available and readily leached under wet conditions
• Ammonium and urea fractions convert to nitrate over time through soil processes
• Contains no phosphorus, potassium, or sulfur

UAN is favoured where liquid handling offers practical advantages, including fertigation, banding with liquid equipment, split in-crop applications on cereals, and blending with certain crop-protection or micronutrient products. It can be dribble-banded or injected to reduce contact volatilisation and foliar scorch.

• Suited to fertigation, banding, and split in-season nitrogen applications
• Can be co-applied with some other liquid inputs where compatibility is confirmed
• Dribble-banding or incorporation reduces volatilisation from the urea fraction

UAN solutions are corrosive to mild steel and some other metals, so storage and application equipment must use compatible materials or corrosion inhibitors. Foliar contact can scorch leaves, and the urea fraction is subject to ammonia volatilisation when left on the surface without incorporation or timely rainfall.