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Spreading urea: how wide can you go, and what are the rules?

Urea is cheaper per kilogram of nitrogen, but it’s harder to spread wide and easier to lose to the air. What decides how wide you can go, and the rules on when you can use it.

By Spreadcheck, NSTS testers. Published . 8 minute read.

The short answer

Narrower than ammonium nitrate, unless the urea is large-granule and the spreader has the discs for it. Urea weighs about 0.75 kg a litre against about 1.0 kg for CAN, so it doesn’t throw as far, and in England unprotected solid urea can only be spread from 15 January to 31 March under the industry scheme Defra accepted instead of a ban, enforced through Red Tractor.

  • Urea is 0.7–0.8 kg a litre against about 1.0 kg for CAN, so it is harder to throw and usually can’t be spread as wide.1
  • Teagasc says small prilled urea is particularly hard to spread on bouts over 10 m.2 One spreader manufacturer lists its 36–42 m discs for urea granules larger than 2.9 mm.3
  • Red Tractor (England): unprotected solid urea only between 15 January and 31 March; outside that, it must be protected, for example with a urease inhibitor. It covers any fertiliser with 1% or more nitrogen as urea.45
  • RB209 says 10–30% of urea’s nitrogen is typically lost as ammonia.6 Defra says urease inhibitors cut that by 70% on average.7
  • Protected urea can spread differently from plain urea, especially where the inhibitor was sprayed on after the urea was made: Rauch says it can build up on the vanes and change the pattern.8
  • Urea is more sensitive to wind than other fertilisers, according to Rauch, and blends of urea with denser products can separate across the bout.910

Why urea won’t throw as far

A spinning disc throws every granule at about the same speed. After that, it’s air resistance against weight. Urea granules are lighter for their size than ammonium nitrate or CAN, so they slow down sooner and land shorter.

  • Density. Urea weighs about 0.7–0.8 kg a litre against about 1.0 kg for CAN.1 A bulk bag that holds 500 kg of CAN holds only about 375 kg of urea.11
  • Size. Bigger granules fly further. Teagasc says small prilled urea is particularly hard to spread on bouts over 10 m, and wants 80% of granules between 2 and 4 mm for wider bouts.2 In studies reviewed at Wageningen, granular urea spread about 20 m where prilled urea spread about 10 m.12
  • Strength. Teagasc wants urea crush strength above 5 kg, and never below 3 kg.13 Soft granules break on the vanes and the pieces land short.14

Rauch’s manual notes that urea comes in a wide variety of qualities and granule sizes, so the settings may need adjusting from one to the next.9 That’s why the bout width that works for one urea won’t necessarily work for another.

How urea is protected

There are two ways to get a urease inhibitor into urea. It can be dissolved into the molten urea before it’s granulated, so it ends up inside every granule, or it can be applied afterwards as a liquid on the finished granules.15 For the second route, the liquid is typically sprayed onto the granules as they tumble in a mixer until it’s spread evenly over their surface.16 BASF says its Limus is applied at a partner’s plant before bagging, and that it soaks into the granule rather than sitting on the surface as a coating.17 Treated urea is usually dyed so you can tell it from plain urea.17

Why protected urea can spread differently

A spinning disc throws granules by their surface, and applying the inhibitor afterwards changes that surface. What the evidence says:

  • Build-up on the vanes. Rauch told customers in 2023 that inhibitor sprayed on after manufacture can settle on the vanes during spreading and form a layer that changes how the granules flow and spread. It advised checking the setting with trays only after about 200 kg has gone through each disc, once any layer has formed;8 its test kit manual says about 300 kg.18
  • A different surface. SKW Piesteritz, which makes urea with the inhibitor inside the granule, says spraying changes the granule’s surface and so the angle at which it strikes the vane, and that no spreader manufacturer has setting charts specifically for sprayed urea.19 SKW has a commercial interest in saying so, but it matches Rauch’s warning.
  • Stickiness. A patent for one spraying method notes that if the amount of liquid isn’t well controlled, a flow aid such as gypsum or clay may be needed to keep the treated granules flowing, and that too much liquid left the product too wet to use.16
  • Strength. The inhibitor doesn’t fix a weak base product. Teagasc says protected urea is only as good as the urea it’s made from,20 and Irish farmers testing protected urea in 2024 often found granules far softer than Teagasc’s minimum.1413

Not all build-up comes from the inhibitor. Urea leaves residue on vanes more than most fertilisers, and BASF’s UK distributor says the yellow dye in Limus can make build-up look worse than it is.17 Teagasc’s view is that excessive deposits on the vanes point to poor physical quality, and will cause uneven spreading.20

What nobody has published is how much each treatment changes the throw. We looked for independent measurements of spread width or vane grip for inhibitor-treated urea and didn’t find any. Products differ in how they’re treated and what with, so protected urea needs setting and testing as its own product: run a couple of hundred kilos through each disc first, then put the trays down.

How wide can you go?

There’s no single answer, because it depends on the urea and on the spreader:

  • Small prills: Teagasc says they’re particularly difficult beyond 10 m.2
  • Good granular urea, 2–4 mm: suits wider bouts on a modern twin-disc spreader set for urea.2
  • 36 m and over: Rauch, for example, lists its 36–42 m disc set for urea granules larger than 2.9 mm, and separate discs for 24–36 m.3 We tray test urea at 36 m regularly, and it’s the product and the disc set that decide whether it gets there.

If your tramlines are set for a sprayer at 36 m and your urea won’t reach, you have two honest choices: a narrower bout for the urea, driving extra passes, or a urea and a disc set that are proven to reach. A tray test at your width, with your urea, tells you which.

The urea rules: industry scheme, not law

The urea rules in England started as a Defra consultation, which is why many people assume they’re law. They aren’t. Defra consulted on a ban or restrictions in 2020–21, then accepted the fertiliser industry’s alternative, a self-regulation scheme the AIC calls Option 4, delivered through Red Tractor.2122 Since 1 April 2024, Red Tractor standard UR.1 has applied to solid urea in England:45

  • 15 January to 31 March: unprotected solid urea may be used.
  • The rest of the year: solid urea must be protected, for example with a urease inhibitor, which slows the conversion that releases ammonia.
  • What counts as urea: any fertiliser with 1% or more of its nitrogen as urea, so compounds and blends containing urea are caught too.

The same rule is in Red Tractor’s Dairy, Beef & Lamb and Pigs standards, so grassland urea on assured livestock farms is covered.5 Liquid fertilisers with more than 1% urea need protection from 1 April to 15 January too.23 Defra said it would monitor the scheme and decide whether to bring in regulation in 2025/26; at the time of writing we haven’t found a published decision.21 In England in 2025, about a third of the urea spread after March was still unprotected.24 Wales, Scotland and Northern Ireland follow their own rules; Northern Ireland has proposed its own 1 February to 31 March window from 2027.525

Keeping the nitrogen

Some of urea’s nitrogen is lost to the air as ammonia before the crop can use it. RB209 puts it at typically 10–30%, depending on soil and weather;6 Defra’s ammonia code says up to 45% in poor conditions, against up to about 2% for ammonium nitrate.7

  • Pick the weather. Defra advises spreading urea when soils are moist but not wet, or when rain is expected, and avoiding dry spells.7 Teagasc found 7–14 mm of rain soon after spreading cut losses sharply.2
  • Use an inhibitor. Urease inhibitors cut ammonia from solid urea by 70% on average, according to Defra.7
  • Remember the March window isn’t a guarantee. A dry March can still bring high losses.

Wind and blends

Light granules suffer most in a side wind. Rauch’s manual says urea is more sensitive to wind than other fertilisers,9 and its wind tool judges the wind across the direction of travel, because that’s what shifts the pattern.26 In New Zealand tray tests on DAP, a denser product than urea, a 6 m/s cross wind cut the usable bout width from 21 m to 13 m.27 There’s no official UK wind-speed limit for spreading; Defra’s code simply says not to spread in very windy conditions that disrupt the pattern.28

Blends of urea with dense phosphate and potash products are harder still. The light urea and the heavy ingredients land at different distances, so the nutrients separate across the bout. Teagasc advises caution with them.10

Other questions people ask

Can you spread urea at 36 m?

It can be done, but it depends on both the product and the spreader. Rauch lists its 36–42 m disc set for urea granules larger than 2.9 mm,3 and small prills won’t get near it.2 We tray test urea at 36 m regularly, and the only way to know for your spreader and your urea is to tray test it at that width.

Is the urea rule the law?

No, it’s an assurance standard. Defra consulted on a ban or restrictions, then in 2022 accepted the industry’s proposal to use Red Tractor instead, and said it would consider regulation if ammonia emissions didn’t fall enough.21 The rule applies in England; Wales, Scotland and Northern Ireland follow their own rules, and Northern Ireland has proposed its own window from 2027.525

Should I spread urea before rain?

Light rain soon after spreading helps. Defra’s ammonia code says to plan urea when soils are moist but not wet, or when rain is expected, and to avoid dry spells.7 Teagasc found 7–14 mm of rain soon after application gave large reductions in loss.2 Heavy rain brings its own risk of run-off.

Does protected urea spread differently?

It can do, and how much depends on how it was protected. The inhibitor is either mixed into the urea before it’s granulated, or applied afterwards as a liquid on the finished granules.15 Rauch has warned that inhibitor sprayed on afterwards can build up on the vanes and change the spread pattern, and advises checking the setting only after about 200 kg per disc.8 Nobody has published how much each product changes the throw, so set and test the spreader for protected urea separately from plain urea.

About this article

Written by Spreadcheck (Spreader & Sprayer Testing Ltd), an NSTS testing company at Rookery Farm, Wheaton Aston, Staffordshire, which wrote the original qualification for fertiliser spreader and slug pelleter testing that NSTS adopted. We sell testing, so every figure here links to its source, and we say where the evidence is mixed.

Checked on 12 October 2026. Rules, prices and guidance change, so follow the links for the latest.

Sources

  1. Teagasc and the Fertilizer Association of Ireland, Precise Application of Fertiliser, Technical Bulletin 3, 2017.
  2. Teagasc, Urea N fertiliser factsheet, 2016.
  3. Rauch, AXIS 25 brochure, 2025.
  4. Red Tractor, Combinable Crops and Sugar Beet Standards, version 5.1, EC.7 and EC.10, February 2025.
  5. Red Tractor, Urea standards (UR.1) across the Crops, Dairy, Beef & Lamb and Pigs schemes, accessed 2026.
  6. AHDB, Nutrient Management Guide (RB209), Section 1: Principles of nutrient management and fertiliser use, 2026.
  7. Defra, Code of Good Agricultural Practice for reducing ammonia emissions, section 4, updated 2024.
  8. Rauch, notice of 16 February 2023, reproduced in an SKW Piesteritz presentation (LfULG field day, January 2024), slide 16, Vorsicht bei Harnstoffen mit Ureaseinhibitoren (caution with urea containing urease inhibitors), in German, 2023.
  9. Rauch, AXIS 20.2 to 50.2 instruction manual, section 8.6, 2015.
  10. Teagasc (Dermot Forristal), Accurate spreading: six steps you need to take, Today’s Farm, 2023.
  11. Irish Farmers Journal, Urea v compound: do you know how to set your spreader accurately?, 2026.
  12. J. W. Hofstee, Wageningen University, Physical properties of fertilizer in relation to handling and spreading (PhD thesis), 1993.
  13. Teagasc, Key points for spreading protected urea, 2025.
  14. Irish Farmers Journal, Is protected urea a runner in 2025?, 2025.
  15. BASF SE, EP 4423040 A1: Urease inhibitor formulation for use in urea granulation process, 2024.
  16. Whitehurst Associates, US 8,163,058 B2: Amino alcohol solutions of NBPT and urea fertilizers using such solutions as urease inhibitors, 2012.
  17. Thomas Bell (Diamond Fertilisers), UK distributor of Limus-treated urea, Limus FAQs, 2024.
  18. Rauch, Practical test kit operator’s manual, 2024.
  19. SKW Stickstoffwerke Piesteritz (Marcel Titze), LfULG field day; SKW makes urea with the inhibitor inside the granule, Die Bedeutsamkeit einer hohen Düngemittelqualität (the importance of high fertiliser quality), slide 21, in German, 2024.
  20. Teagasc, Fertiliser focus: urea, even spread is essential, Today’s Farm, 2022.
  21. Defra, Reducing ammonia emissions from solid urea fertilisers: government response, 2022.
  22. Agricultural Industries Confederation, Urea Option 4: ammonia mitigation, accessed 2026.
  23. NFU, Applying urea after 1 April: new urea rules, essential information, accessed 2026.
  24. Defra, British Survey of Fertiliser Practice, crop year 2025, statistics notice, Table C4.1e, 2026.
  25. DAERA (Northern Ireland), Consultation on the Nutrients Action Programme 2027–2030, 2026.
  26. Rauch, WindMeter press release, 2020.
  27. Grafton et al., Massey University FLRC, Occasional Report 29 (NZ Spreadmark field trials in slope and wind), 2016.
  28. Defra, Protecting our Water, Soil and Air: Code of Good Agricultural Practice, paragraph 434, 2009.