Nitrogen
Urea vs ammonium sulphate: which is cheaper per kg of N?
By the Fert Directory editorial team · Published 17 October 2026 · Last updated 17 October 2026 · Not yet reviewed by a qualified agronomist
Direct answer
Urea carries more nitrogen per tonne (46% N against about 20–21% for ammonium sulphate), so it usually costs less per kilogram of N. Ammonium sulphate also supplies sulphur and, on non-calcareous soils, loses less N to the air. On soils with free lime the loss reverses and ammonium sulphate can lose more than urea.
Key numbers
| What | Figure | Source |
|---|---|---|
| Granular urea NManufacturer product card, our data | 46% N | Arithmetic / our data |
| Gran-Am (ammonium sulphate) N and SManufacturer product card, our data | 20.2% N, 24% S | Arithmetic / our data |
| Sulphate of ammonia N | 21% N (older state bulletin) | DPIRD Digital Library 1994 |
| Surface loss, ammonium sulphate vs ureaNorthern NSW study | less than half on non-calcareous soil | GRDC 2021 |
| Ammonium sulphate on soils with more than 10% calcium carbonate | 19–34% N loss on fallow soils | GRDC 2021 |
| Ranking in southern Australian trials | urea > UAN > ammonium sulphate (loss 1.8–23% of N) | Nutrient Cycling in Agroecosystems 93, 113–126 (peer-reviewed) 2012 |
Nitrogen and sulphur per tonne
The analysis on the bag decides how much you cart and spread. To supply 50 kg of N per hectare you need about 109 kg/ha of granular urea (50 ÷ 0.46), or about 248 kg/ha of Gran-Am (50 ÷ 0.202). The Gran-Am rate also carries roughly 59 kg/ha of sulphur (248 × 0.24), which urea does not supply. See the granular urea and Gran-Am pages for the published analysis and sources.
Cost per kilogram of N
Cost per kg N = price per tonne ÷ (10 × N%). We only have one source for prices: a set of listings read on 17 October 2026 (asking prices, ex GST, not quotes, no listing date). Both lines below are Geelong listings from that same page.
| Product | Listed price | N % | Cost per kg N |
|---|---|---|---|
| Urea | $820/t | 46% | $1.78 |
| Sulphate of ammonia (44 t lot) | $540/t | 21% if the older DPIRD figure applies (the listing did not state N %) | $2.57 |
On those two listings urea is cheaper per kg of N. The ammonium sulphate line is only indicative because the listing did not give its N percentage, and the price covers a large lot. The extra cost buys sulphur, so judge it against your sulphur need and soil test, not nitrogen alone.
Nitrogen lost to the air
- In a northern NSW study summarised by GRDC, ammonium sulphate lost less than half as much N as urea on non-calcareous soils.
- On fallow soils with more than 10% calcium carbonate the same study measured 19–34% loss from ammonium sulphate, higher than urea.
- Incitec Pivot Fertilisers (a manufacturer) says swapping urea for ammonium sulphate is not advised where soil has free lime (more than 2% CaCO3).
- Southern Australian trials by Turner and colleagues ranked loss as urea, then UAN, then ammonium sulphate, from 1.8 to 23% of N applied.
Loss is not the only pathway, and one study does not make a rule for your paddock. Read how much N you really lose from urea for what drives it.
Soil acidification
A 1994 Western Australian bulletin describes sulphate of ammonia as strongly acidifying, and notes urea and ammonium nitrate also acidify. That bulletin is old, so treat it as background and monitor soil pH with your own tests.
How to choose
- If you only need nitrogen and your soil is not calcareous, compare on effective cost per kg of N, including likely loss. The comparison tool does this arithmetic.
- If a sulphur test says you need S, ammonium sulphate delivers N and S together; compare that against buying S separately.
- If your soil has free lime, be cautious about ammonium sulphate and ask your agronomist.
What we could not verify
- The 21% N figure for sulphate of ammonia comes from a 1994 bulletin; the price listing itself did not state N %, so the $2.57/kg N figure is indicative only.
- We have not published a sulphur-need table: no primary source was read for crop sulphur requirements in this article.
References
- Nitrogen loss pathways. How much N is lost when urea is not mechanically incorporated after application? (Schwenke G (NSW DPI); GRDC Update Papers, 2021; Grower research summary. Checked 2026-10-17.)
- Ammonia volatilization from nitrogen fertilizers applied to cereals in two cropping areas of southern Australia (Turner DA, Edis RB, Chen D, Freney JR, Denmead OT; Nutrient Cycling in Agroecosystems 93, 113–126 (peer-reviewed), 2012; Peer-reviewed paper. Checked 2026-10-17.)
- Planning nitrogen applications and rethinking potential urea nitrogen volatilisation losses (Laycock J (Incitec Pivot Fertilisers); Incitec Pivot Fertilisers (manufacturer; commercial interest in Green Urea NV), 2024; Manufacturer technical article. Checked 2026-10-17.)
- Bulletin 4283 – Nitrogen fertilisers for cereal production (Mason MG (Department of Agriculture Western Australia); DPIRD Digital Library, 1994; State agency bulletin (historic; prices and rates are dated). Checked 2026-10-17.)
- Farm Inputs (Farm Tender) fertiliser listings: Urea ex Geelong, Brisbane, Port Kembla, Newcastle; SOA ex Geelong (Farm Inputs / The Farm Trader Australia Pty Ltd; Farm Tender (commercial listing page), 2026; Retail listing (price data, not research). Checked 2026-10-17.)
More on how we check sources: methodology. Spot an error? Tell us.
General information only. Check with your agronomist or local advisor. More