Urea vs UAN: does the liquid premium pay?

What the trials found

A GRDC update paper by McDonald and Hooper found no consistent difference between forms of N when compared at the same rate and time. Across trials on Eyre Peninsula, Yorke Peninsula, Hart and Birchip from 2000 to 2010, yields with UAN were not significantly different from yields with urea.

In Western Australia, 40 wheat and canola trials gave 132 side-by-side comparisons, and average yields differed by less than 1%. Where single wheat comparisons did differ, they went both ways: 11 favoured UAN (4–17% higher) and 9 favoured urea. Those authors worked for CSBP, which sells UAN. A Birchip Cropping Group trial in a dry season with high soil N also found no yield or protein difference between urea, ammonium nitrate and UAN.

Nitrogen per tonne, per litre and per hectare

Liquid N is sold by weight but applied by volume, and labels quote two figures. Summit lists UAN as 32% N weight for weight (w/w) and 42.2% weight for volume (w/v). The bigger number is per litre, not per tonne. Always check which one a price or rate uses.

The urea and UAN rates match Summit's own rate table. See the granular urea, Summit UAN and EASY N pages for each published analysis and source.

The liquid premium: what UAN must cost to match urea

We hold no verified UAN price, so here is the break-even instead. Cost per kg N = price per tonne ÷ (10 × N%). For UAN at 32% w/w that is price ÷ 320. So UAN matches urea per kg of N when its price per tonne equals urea's cost per kg N × 320.

If a UAN quote per tonne is above the right-hand figure, you are paying a premium per kg of N delivered, and the liquid has to earn it back through logistics or timing. The 8.1% is the median in-crop urea loss in a GRDC summary; halving it for UAN is our assumption, based on the GRDC paper's note that UAN losses run at about half the urea rate. Work through the arithmetic in cost per kg of nitrogen.

Nitrogen lost to the air

• McDonald and Hooper rank volatilisation risk highest for urea and lower for UAN and ammonium sulphate. Victorian work they cite suggests urea losses of up to 1% a day, and about half that for UAN.
• Southern Australian trials by Turner and colleagues ranked ammonia loss as urea, then UAN, then ammonium sulphate, from 1.8% to 23% of N applied.
• Incitec Pivot says EASY N reduces loss potential compared with dry urea. That is the manufacturer's claim.

Loss depends heavily on soil, moisture and rain after application. Read how much N you really lose from urea before paying extra to avoid it.

Where UAN can earn its keep

• Storage and handling: UAN is stable in bulk tanks and goes on through a boomspray, which the WA authors say gives fast, even application.
• Placement: in the same WA work, banding UAN 30–40 mm below the seed lifted N use efficiency by about 7% on average over boomspraying it.
• Fewer passes: some crop protection products can go on with UAN, but mixing needs care. Birchip found 2,4-D Amine did not mix easily and had to go into water first.
• Leaf scorch: Birchip saw little scorch when UAN was diluted with water, and noted more crop damage in other trial work.

How to choose

• Price both products per kg of N on the same basis (ex GST, delivered, same date). The comparison tool does the sums and adds likely loss.
• Work out your rate first with the nitrogen calculator, then convert to litres for UAN.
• If urea is cheaper per kg of N delivered and you can spread it evenly, the trials give no yield reason to pay more.
• If you already run a boomspray or band at sowing, or urea losses are likely, the logistics may justify a small premium. Ask your agronomist.