Should you tray test a new fertiliser spreader?

The short answer

Yes. Test a new spreader with the fertiliser you’re going to spread, on the tractor that will pull it.

• A setting chart is right for the fertiliser it was made with, in a test hall.^1,2 But fertiliser is a commodity, made all year round in different plants and batches, so the product in your shed may not be the one the chart was made for.^4,11 And the chart can’t know your tractor or your set-up.
• A fertiliser’s chemistry is controlled. Its physical properties aren’t: granule size, density and hardness vary between products and between batches, and they decide how far each granule is thrown.^3,4
• AHDB’s RB209 says to calibrate for rate every spring and whenever you change fertiliser type, and to check the spread pattern with trays every year. The AIC advises a tray test for every new type, brand or batch.^5,1
• New spreaders aren’t usually badly wrong out of the box. But you only know yours is right once it’s been tested.^6,7
• Uneven spreading costs yield where strips are short, and brings lodging, disease, missed grain specifications and nitrate losses where they’re over-fed.^5,8,9

The chart is right for the fertiliser it was made with

Every spreader manufacturer publishes setting charts, and many now put them in an app. They’re made in test halls under controlled conditions, using a sample of each fertiliser.^10,11 Kverneland says the working widths in its charts are the widest that gave under 10% CV in the lab, and that not every fertiliser can be spread at every width.¹¹

The Agricultural Industries Confederation says manufacturers’ tables “give guidance only”.¹ Teagasc and the Fertilizer Association of Ireland describe them as approximate guides, and a starting point.²

That doesn’t make charts bad. In an independent test of seven spreaders at Aarhus University’s Bygholm test hall in 2011, every machine set from its manual scored under 15% CV.⁶ But the same test showed how far a chart can sit from the best setting for one batch of fertiliser.

13.6%CV on chart settings

5.1%CV after a tray test

And that was indoors, out of the wind, on a level floor. Teagasc and the FAI note that test halls achieve under 5% CV, while up to 15% is acceptable in the field.²

No two fertilisers spread alike

A fertiliser’s analysis is tightly controlled: the bag tells you what’s in it. Its physical make-up isn’t. Teagasc puts it plainly: the chemical analysis is controlled, but particle size, shape, strength and density are not, and they have a big effect on how it spreads and on the right setting.³

Those properties decide how a granule leaves the vane and how far it flies.

• Density. Urea weighs about 0.75–0.8 kg a litre, against about 1.0 kg for calcium ammonium nitrate (CAN), and density has a large effect on spread width.¹³ NutriNorm gives typical ranges of 0.97–1.07 kg/l for CAN and 0.70–0.80 kg/l for urea.¹⁴
• Granule size. In studies reviewed at Wageningen University, larger granular urea spread about 20 m where prilled urea spread about 10 m, and the drop point on the disc had to change.¹⁵ Teagasc’s target is 80% of granules between 2 and 4 mm.¹³
• Hardness. Teagasc’s target is a granule strength above 6.¹³ Granules that break up on the vanes don’t fly the distance the setting assumes.
• Blends. When a blend’s components differ in size, they separate. A difference of 0.75 mm in median size raised CV by up to 8 points on twin-disc spreaders.¹⁵

And those properties change between batches of the same product. Yara, which makes fertiliser, says two batches of the same product can need different spreader settings, and that the same product may be made in different factories.⁴ Kverneland says fertilisers sold under the same name can behave differently depending on where they were made, how they were transported and stored, and the humidity. It advises identifying a fertiliser by its granule size and specific weight, not its name.¹¹ Amazone says physical properties strongly affect both how evenly a fertiliser spreads and how much comes out.¹⁶

Storage counts too

Quality can deteriorate in transport, storage and handling.¹⁴ Damp makes granules soft and sticky, increases caking and dust, and can affect spreading quality.¹⁷ Yara UK advises stacking bags no more than three high, and says old stock may need different settings.⁴ Nobody has published how much a particular shed changes a particular batch. You find that out by testing.

A new spreader still needs checking on your farm

A new spreader arrives with the manufacturer’s settings and a set-up procedure. It doesn’t arrive with your tractor, your fertiliser or your fields. On the day, these all change the pattern:

• Working height above the crop, which shifts with tyre squash, wheel sinkage and tramline depth.¹
• Whether the spreader sits level side to side, and at the front-to-back angle the manufacturer specifies for that product and width.^1,18
• PTO speed at the shaft, and whether the tractor’s rev counter is telling the truth.¹
• Headland settings. The AIC advises a fresh tray test whenever headland equipment is used.¹ Teagasc measured cereal headlands on 17 farms and found the first 8 m got about 20% less than target and the next 8 m about 20% more.³
• The fertiliser in the hopper, for all the reasons above.

Yara’s advice is blunt: even a brand new spreader will need calibrating, and a first tray test can find the starting settings giving a CV of around 30%.¹⁹ To be fair to the machines, that isn’t always the case. A new spreader checked by profi magazine in 2025 was right first time.⁷ The point is that you only know once you’ve checked. In Defra’s latest survey, 2% of farms with a spreader said theirs was factory set and didn’t need checking.²⁰

What uneven spreading costs

A spreader with a poor CV doesn’t put on the wrong total. It puts too little on some strips and too much on others, and the two don’t cancel out.

Where it’s short: lost yield and quality

A crop’s response to nitrogen is curved: each kilogram short of the optimum costs more than the last. RB209 sets out the yield lost by applying less than the optimum:⁸

On a 200 kg N/ha wheat dose, a strip getting 20% too little is 40 kg short. Protein suffers too: RB209 says an extra 40 kg N/ha can lift grain protein by up to 0.5%, so a strip that is 40 kg short can miss a milling specification as well as losing yield.⁸

Where it’s over: lodging, disease, specifications and losses

Above the optimum the response curve flattens, so the extra nitrogen on over-fed strips doesn’t win back what the short strips lost.⁵ It brings risks of its own.

• Lodging and disease. RB209 says too much nitrogen can cut yield by making lodging and foliar disease worse.⁵ AHDB says lodging around ear emergence can cut yield by up to 75%, lowers Hagberg and specific weight, and adds drying costs.⁹ For oilseed rape, excess nitrogen encourages disease, delays maturity and reduces oil content.⁸
• Malting barley. Maltsters buy on tight grain nitrogen bands: 1.60–1.75% for UK brewing, 1.70–1.85% for export brewing, and up to 1.65% for distilling. Loads outside specification face scaled deductions, with rejection as a last resort.²¹ RB209 says about 30 kg N/ha moves grain nitrogen by about 0.1 percentage point.⁸
• Water and air. Nitrogen above the optimum leaves more nitrate in the soil after harvest, at risk of leaching and of loss as nitrous oxide.⁵ Fertiliser thrown into the 2 m strip beside a watercourse breaks the rules for nitrate vulnerable zones and the Farming Rules for Water.^22,23

In money

At a moderate CV the loss per hectare is modest. It grows quickly as the CV rises, and quickly again across a whole farm.

• Ecopt put a 20% CV at £8.79/ha and a 30% CV at £17.80/ha in winter wheat, at 2012 prices of £350/t for ammonium nitrate and £165/t for wheat.²⁴
• The Farm Advisory Service in Scotland puts a 25% CV, which it says is often found before testing, at about £20/ha of margin in wheat and winter oilseed rape, compared with the 5% a test can achieve. It found a professional test pays for itself in about 12 hectares.²⁵
• Yara, which sells fertiliser, puts accurate spreading at £20–100/ha from yield alone, depending on how responsive the site is to nitrogen.²⁶

Those figures were worked out when fertiliser was cheaper. UK-produced ammonium nitrate cost £485/t in the week to 2 October 2026, after rising 25% in March.²⁷ AHDB’s harvest 2027 budgets put fertiliser at £407/ha for winter feed wheat, more than half its variable costs.²⁸ The average English cereal farm spent £35,500 on fertiliser in 2024/25, and £57,300 the year before.²⁹

To put a figure on it for your own crops, spreader and fertilisers, use our spreader test calculator. It shows its working.

Reading a CV, and why stripes are the last thing you see

The coefficient of variation (CV) measures how evenly a spreader puts fertiliser across the working width. A tray test catches what lands in trays across the full spread, overlaps the passes, and works out how far each tray strays from the average. The lower the CV, the more even the spread.

Sources disagree about exactly when stripes appear, but not about what matters: yield is lost before you can see anything. NSTS says a crop without stripes is no guarantee of an even spread.³¹

How often to test: the law, assurance and advice

Our view: test before the season with each fertiliser you plan to spread, and again after any work on the discs or vanes. Between tests, check each new delivery against the one you tested.

What farms actually do

Defra’s British Survey of Fertiliser Practice asks farms with a spreader how often they check the spread pattern with trays.²⁰

Most farms check once a year. Only about one in seventeen checks when the fertiliser changes, which is when the guidance says it matters most.

Between tests: checking a new delivery

A full tray test for every load isn’t practical, and most advisers don’t ask for one. Teagasc’s approach is to characterise every batch, with a sieve box for granule size, a measured volume for density and a strength test, and compare it with the fertiliser the settings were made for.³ If the new delivery is different, the settings need checking. A small set of trays lets you spot-check the pattern without waiting for a full test.

What happens on an SCS spreader test

1. The machine. An MOT-style check of the spreader, including the tractor’s PTO speed.
2. Your fertiliser. We measure its bulk density, crush strength and granule size.
3. The tray test. Trays every metre across the full width. We adjust the spreader until the pattern is right for that product.
4. The report. An NSTS report with the settings, photos and the conditions on the day, emailed to you and uploaded to the NSTS database.

The NSTS fertiliser spreader test covers inspection of the spreader, tray testing across the working width, and adjustment for the best CV for each product.³⁶ SCS wrote the original qualification for fertiliser spreader and slug pelleter testing that NSTS adopted.

Book a spreader test

We test fertiliser spreaders, sprayers, slug pelleters and granular applicators anywhere in the UK. Ring the office and we’ll find a date before your first application.

01785 840 849 Request a booking

About this guide

Written by Spreadcheck (Spreader & Sprayer Testing Ltd), an NSTS testing company at Rookery Farm, Wheaton Aston, Staffordshire. We sell spreader testing, so every figure here links to its source, and we say where the evidence is mixed: for example, no UK law requires a fertiliser-only spreader to be tested, and many new spreaders are close on their chart settings.

Figures were checked on 10 October 2026. Prices and survey results change; follow the source links for the latest.

Sources

1. Agricultural Industries Confederation, Fertiliser Spreaders: choosing, maintaining and using, 2005, linked from RB209 2026.
2. Teagasc and the Fertilizer Association of Ireland, Precise Application of Fertiliser, Technical Bulletin 3, 2017.
3. Teagasc (Dermot Forristal), Accurate spreading: six steps you need to take, Today’s Farm, 2023.
4. Yara UK, Spreading preparation, accessed 2026.
5. AHDB, Nutrient Management Guide (RB209), Section 1: Principles of nutrient management and fertiliser use, 2026.
6. Farmers Weekly, Searching for the best fertiliser spreader (Bygholm test hall), 2011.
7. profi, Amazone ZA-TS 5000 fertiliser spreader test, 2025.
8. AHDB, Nutrient Management Guide (RB209), Section 4: Arable crops, 2026.
9. AHDB, An introduction to lodging in cereals, accessed 2026.
10. Yara UK, Spreader calibration, accessed 2026.
11. Kverneland, Kverneland spreading charts, accessed 2026.
12. Farmers Weekly, Fertiliser spreader test: Amazone ZA-M, 2011.
13. Teagasc, Fertiliser spreader tray test and field procedure, leaflet 16, 2025.
14. NutriNorm (OCI Nitrogen), Quality of fertilisers, accessed 2026.
15. J. W. Hofstee, Wageningen University, Physical properties of fertilizer in relation to handling and spreading (PhD thesis), 1993.
16. Amazone UK, Conscientious fertiliser spreading, accessed 2026.
17. Yara, Physical properties of fertilizers, accessed 2026.
18. Teagasc, Fertiliser spreader basic set-up and calibration, leaflet 15, 2025.
19. Farmers Weekly, How to calibrate your fertiliser spreader for grass (Yara advice), 2008.
20. Defra and Scottish Government, British Survey of Fertiliser Practice: fertiliser use on farm crops for crop year 2025, Section C1, 2026.
21. Maltsters’ Association of Great Britain, Barley requirements, accessed 2026.
22. gov.uk, Using nitrogen fertilisers in nitrate vulnerable zones, 2024.
23. gov.uk, Rules for farmers and land managers to prevent water pollution, 2026.
24. Farmers Weekly, Correct application makes the most of fertiliser (Ecopt figures), 2012.
25. Farm Advisory Service (Scotland), Fertilisers and spreader calibration, 2018.
26. Yara UK, How much can you actually save?, accessed 2026.
27. AHDB, GB fertiliser prices, week to 2 October 2026.
28. AHDB, Analyst insight: will wheat still lead for harvest 2027 gross margins?, 2026.
29. Defra, Farm Business Survey: Farm Accounts in England 2024/25, Table 5.3, 2026.
30. Teagasc, Fertiliser calibration, 2023.
31. Farm Contractor & Large Scale Farmer, AEA to launch National Spreader Testing Scheme, 2015.
32. legislation.gov.uk, The Water Resources (Control of Agricultural Pollution) (Wales) Regulations 2021, Part 4, 2021.
33. legislation.gov.uk, The Plant Protection Products (Sustainable Use) Regulations 2012, regulation 12, 2012.
34. NSTS, Slug pellet applicator test, accessed 2026.
35. Red Tractor, Combinable Crops and Sugar Beet Standards, EC.7 and EC.10, 2025.
36. NSTS, Fertiliser spreader test, accessed 2026.