Spreading questions, answered

The questions farmers ask us, and ask Google, about fertiliser spreaders, tray tests and the rules. Each article starts with the short answer, then the detail, with every source linked.

By Spreadcheck, NSTS testers. Updated 12 October 2026.

Start here

• Should you tray test a new fertiliser spreader?

  Yes. The long read: what AHDB, the AIC, fertiliser manufacturers and spreader manufacturers say, what uneven spreading costs, and how often to test, with 36 sources.

Testing and the rules

• How often should a fertiliser spreader be tested?

  Once a year, plus a rate check whenever the fertiliser changes. What the law, Red Tractor, RB209 and the AIC each actually say.

• How much does an NSTS spreader test cost?

  What happens on the test, what you get, and how quickly it pays back. Contact us for a quote.

• What is a good CV for a fertiliser spreader?

  Under 10% is very good, up to 15% is acceptable. What the number on a tray test report means on the ground, and why it only holds for one fertiliser and one width.

• Can you tray test your own spreader?

  Yes, as a check between full tests. What a few trays or mats can tell you, what they can’t, and when you need the full test.

• Do slug pellet applicators need testing?

  Yes: by five years old, then every six. And if your fertiliser spreader puts on pellets, Red Tractor and SQC say it needs the same test.

Setting up and spreading

• Why is my crop striped after spreading fertiliser?

  Where the stripes fall tells you a lot. The usual causes, from bout width to worn vanes, and why yield goes before the stripes show.

• How to calibrate a fertiliser spreader

  The formula, a calculator, and the rate check step by step. Plus the one thing a rate check can’t tell you.

• Spreader setting charts and apps: are they right for your fertiliser?

  Right for the fertiliser they were made with. Fertiliser is a commodity made all year round, so check the setting with yours. Where each manufacturer’s chart and app lives.

• Do spreaders with radar or automatic settings still need tray testing?

  Yes. Amazone’s own manual says a test kit is mandatory with its radar system, and its new self-adjusting spreader still asks for a mat check.

Your fertiliser

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

  Urea is light, so it won’t throw as far as AN. How wide it can go, the Red Tractor 15 January to 31 March rule, and how to keep the nitrogen.

• How do you check fertiliser quality before spreading?

  Granule size, bulk density and hardness decide how far fertiliser flies. How to check a delivery, typical figures, and why blends separate.

Who writes these

Spreadcheck (Spreader & Sprayer Testing Ltd) tests fertiliser spreaders, sprayers, slug pelleters and granular applicators across the UK from Rookery Farm in Staffordshire. We wrote the original qualification for fertiliser spreader and slug pelleter testing that NSTS adopted.

We sell testing, so we link every figure to where it came from, and we say so when the evidence doesn’t back us up. Got a question we haven’t answered? Ring 01785 840 849 or email info@spreadcheck.com.