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What is a spreader test worth to your farm?

It takes a minute to complete – we’ve filled in a typical arable farm to start you off.

What could be happening

Most spreaders don’t spread as evenly as they look. On farm we usually find a CV of about 25%: across the bout, some strips get around a quarter more than you meant, and some a quarter less.

  • Too little. Those strips lose yield, and the over-fed strips don’t win it back.
  • Too much. More lodging and disease, missed malting and milling specifications, and nitrate lost to leaching.
  • Too wide or too narrow. Throwing past or short of your tramlines can nearly double the CV.

You can’t see any of it from the cab. The calculator below puts a figure on it for your farm.

Bars across the bout rise above and fall below a dashed line marking your rate. Where they fall short the gap is gold; where they overshoot the extra is dark. Your rate Too much Too little Across the bout, passes overlapped
An illustrative spread at about a 22% CV: gold where strips fall short of your rate, dark where they get too much.

Work it out for your farm

A free calculator from Spreadcheck. There’s nothing to sign up for and nothing is sent to us: it works out on your phone or computer as you type. We’ve started you on a typical arable farm, so change anything that’s different on yours.

Spreader test calculator

Free to use

Your crops

The crops you spread fertiliser on. Nitrogen rates and prices start at the averages for England. If some of your nitrogen goes on as liquid, put in just the part that goes through the spreader.

Your spreaders

The bout width you spread at. Each spreader is tested and certified separately. Your crops are shared between your spreaders, so a second one adds a test but not more hectares.

Your fertilisers

Each fertiliser is tray tested separately, because each one throws differently. Two are included in the test price.

How even it spreads now

Not sure? Start at 25%: it’s what we usually find on farm, and what the Farm Advisory Service says is often found before a test. If it’s your first test, or you’ve seen striping in the crop, it could be much worse.

After the test, and fertiliser prices

We use 10%: NSTS says a well set-up spreader should give about that. The Farm Advisory Service says 5% is achievable.

Your results, crop by crop

Cost of uneven spreading by crop, now and after a test
CropLost now, £/haAfter a test, £/haSaved a year
Winter wheat, feed74 ha£19£3.1£1,165
Winter barley15 ha£12£1.9£148
Spring barley, feed18 ha£5.9£1.0£88
Winter oilseed rape14 ha£12£2.0£145
Oats9 ha£5.5£0.9£42

Your nitrogen bill is about £28,981 a year. A test costs about 1.0% of it.

Understanding your results

£1,898 a year
What uneven spreading could be costing you. The yield your under-fed strips lose, less what the over-fed strips gain back, across all your crops at your CV now.
£310 a year
What it could cost after a test. A test sets your spreader up for your fertiliser. We assume it gets you to 10%, which NSTS says a well set-up spreader should give.
£1,588 a year
What the test is worth. The difference between the two.

Why a few points of CV matter so much

The cost climbs faster than the CV: double the CV and the loss roughly quadruples. This curve is for winter wheat, feed at 180 kg N/ha and £196/t.

The cost of uneven spreading per hectare, rising more and more steeply as the CV goes up. A gold bar marks the drop from your CV now to your CV after a test. £0£15£30£45£600%10%20%30%40%After, 10%Now, 25%A test saves£16/ha
Lost margin per hectare at each CV. The gold bar is the drop a test takes you down.

What this doesn’t count

The sums only count the yield lost across the bout, so the real cost is likely to be higher. They leave out:

  • Lodging. Over-fed strips lodge first, and lodging around ear emergence can cut yield by up to 75% (AHDB).
  • Grain quality: malting barley nitrogen bands, milling protein, Hagberg and specific weight.
  • Headlands, where Teagasc measured strips getting 20% less and 20% more than target.
  • Nitrate leaching, and driving errors in the field, which push real CVs higher than a tray test shows.
How the sums work, in fullThe model, how it compares with published figures and every source

The cost of uneven spreading

Yield rises with nitrogen and levels off. RB209’s recommendations rest on a “linear plus exponential” response curve:

yield = a + b·rN + c·N

AHDB doesn’t publish the curve’s numbers, so we fitted its shape to RB209’s own table of yield lost below the optimum (Table 4.33). For cereals r = 0.99075 and c = -0.0033; for oilseeds r = 0.99023 and c = -0.0001. Both reproduce the table to within 0.01 t/ha.

Uneven spreading doesn’t change how much you put on. It changes where it lands: some strips get more than your rate and some less. Because the curve bends, the under-fed strips lose more than the over-fed strips gain. We treat the rate across the bout as a gamma distribution with your CV, a skewed curve that never goes below zero; a normal distribution gives almost the same answer. That gives the loss directly:

loss, £/ha = (PN − c·PG) ÷ |ln r| × (G − 1)

G = (1 − N·CV²·ln r)−1/CV² ÷ rN

N is your nitrogen rate in kg/ha, PN the cost of nitrogen in £/kg N, and PG your crop price in £/t. The sum assumes your rate is about right for today’s prices, which is what RB209 aims for. That’s why your yield doesn’t appear in it: at the right rate, the last kilogram of nitrogen is worth what it costs, so the loss depends on the shape of the curve, your rate and the prices.

Checking it against published figures

At 2012 prices and 150–180 kg N/ha, this method gives £6–9/ha at a 20% CV and £14–20/ha at 30%; Ecopt’s estimates were £8.79 and £17.80. At today’s prices, 25% against 5% comes to about £18/ha in feed wheat; the Farm Advisory Service put it at about £20/ha in 2018.

SCS test reports use a sharper wheat curve, the one behind the FACTS/Ecopt calculator that NSTS publishes. It gives about 23% more at today’s prices. Here we use the more cautious RB209 shape.

The cost of a test

We price a test by bout width and the number of fertilisers, plus the NSTS certificate. Contact us for a quote.

For the evidence on why charts and new spreaders still need testing, read our guide to spreader testing.

The typical farm we start you on

The average English cereal farm in Defra’s Farm Business Survey 2024/25 has 173 ha of tillage, about 130 ha of it cereals and oilseed rape. We split that 130 ha in line with England’s cropping on 1 June 2026. Nitrogen rates are the average applied in the British Survey of Fertiliser Practice (crop year 2025). Prices are AHDB’s harvest 2027 budget prices, with oats at AHDB’s August 2026 ex-farm price. Ammonium nitrate is £485/t (AHDB, week to 2 October 2026); nitrogen in sulphur products and compounds is priced at the same rate per kilogram.

Sources

  1. AHDB, Nutrient Management Guide (RB209) Section 4, Table 4.33, 2026.
  2. HGCA (Sylvester-Bradley et al.), PR438: the linear-plus-exponential response curve behind RB209, 2008.
  3. Defra, Farm Business Survey, Farm Accounts in England 2024/25, 2026.
  4. Defra, Cereal and oilseed areas in England at 1 June 2026, 2026.
  5. Defra, British Survey of Fertiliser Practice, crop year 2025, 2026.
  6. AHDB, Harvest 2027 crop budgets, June 2026.
  7. AHDB, Corn Returns ex-farm prices (oats), August 2026.
  8. AHDB, GB fertiliser prices, week to 2 October 2026.
  9. Farm Advisory Service (Scotland), Fertilisers and spreader calibration, 2018.
  10. LfULG Sachsen (P. Müller), Tray tests on 11 farm spreaders, before and after setting up, 2017.
  11. Tried & Tested / NSTS, National Spreader Testing Scheme, accessed 2026.
  12. Šima et al., Engineering for Rural Development, Effect of bout spacing on fertiliser spreading uniformity, 2013.
  13. Teagasc, Fertiliser calibration, 2023.
  14. Teagasc and the Fertilizer Association of Ireland, Precise Application of Fertiliser, 2017.

Questions

How much does a fertiliser spreader test cost?

It depends on the bout width and how many fertilisers you want tested. Contact us for a quote: ring 01785 840 849 or email info@spreadcheck.com.

Is a spreader test worth the money?

For a typical arable farm, yes, several times over. On the 130 hectares of cereals and oilseed rape on an average English cereal farm, a spreader at a 25% CV could be costing about £1,898 a year in lost margin. A test that brings it to 10% is worth about £1,588 a year, before counting lodging, grain quality or headlands. The Farm Advisory Service in Scotland found a professional test pays for itself in about 12 hectares.

What CV does an untested spreader have?

There is no UK survey. The Farm Advisory Service in Scotland says a CV of around 25% is often found before testing, against the 5% a test can achieve. In Saxony, 11 farm spreaders tray tested before setting up averaged 24.7%. NSTS says 20–25% is common by the end of a season, against about 10% for a well set-up spreader. AHDB’s RB209 says anything over 15% is a significant inaccuracy.