Fertilizer Spreader Calibration & Hit the Right kg/ha
Calibrates broadcasters
Calibrate your spreader in minutes — from a measured strip test get the real application rate in kg/ha, how it compares to your target, and the total fertilizer for your field.
Enter your spreader test
Next: you're on target — keep this gate setting and ground speed; re-check if you change product, speed or terrain.
rate = applied ÷ area covered (length × swath).
Spreader calibration — key facts
- Rate
- applied ÷ area covered
- Area covered
- length × swath
- 1 ha
- = 10,000 m²
- Open gate
- more rate
- Slow down
- more rate
- Strip length
- ≈ 25–50 m
- Re-calibrate
- each season & product
- Privacy
- Runs in your browser; nothing uploaded
Spread the right rate, not a guess
A spreader chart gets you close, but the real rate depends on the product's density and flow, machine wear, your speed and the gate setting — so without a quick calibration you can easily be 20–30% off. Over-apply and you waste expensive fertilizer and risk lodging or scorch; under-apply and you leave yield in the field. A simple strip test removes the guesswork.
This tool turns that test into the real application rate in kg/ha and kg/acre, shows how it compares to your target, and gives the total fertilizer and bags for your field. Adjust the gate or speed, re-test, and you'll hit the target dose every pass. Re-calibrate each season and whenever you switch product. Pair it with the Fertilizer (NPK) and Lime Requirement tools to set the target rate.
Stop wasting fertilizer
Catch a spreader that's 20–30% over before it costs you.
Protect the yield
Make sure the crop actually gets its recommended dose.
Dial in the setting
See whether to open/close the gate or change speed.
Buy the right amount
Get the field total and bags from your calibrated rate.
Frequently Asked Questions
How do I calibrate a fertilizer spreader?+
Run the spreader over a measured strip (length × swath width), weigh the fertilizer it actually put down, then divide by the area to get kg/ha: rate = applied ÷ (length × swath ÷ 10,000). Compare to your target and adjust the gate or speed. This tool does the maths and shows how far you are from target.
Why calibrate a broadcast spreader?+
Spreader charts are only a starting point — actual rate varies with the product's density and flow, machine wear, ground speed and gate setting. Without calibration you can be 20–30% over or under, wasting fertilizer or starving the crop. A two-minute strip test fixes it.
What is application rate?+
It's the amount of product applied per unit area, usually kg/ha (or kg/acre). Your target comes from a soil test or the recommended dose; calibration makes sure the machine actually delivers it. The tool reports the measured rate in both kg/ha and kg/acre.
How do I adjust the rate?+
To apply more, open the gate/aperture wider or slow down; to apply less, close the gate or speed up. Pressure and impeller/spinner speed also matter on spinner spreaders. Re-run the strip test after each change until the measured rate matches the target.
What strip length and swath should I use?+
Use a realistic working swath width (the effective spread, not the throw) and a measured strip long enough to put down a weighable amount — often 25–50 m. Bigger areas average out variation. Enter your actual strip length and swath and the tool computes the area covered.
How much fertilizer do I need for the whole field?+
Once the rate is right, multiply by the field area: total = rate (kg/ha) × area (ha). The tool gives the field total and the number of 50-kg bags from your calibrated rate and field size, so you can buy and load the right amount.
Does spread pattern matter as well as rate?+
Yes — even at the right total rate, an uneven pattern leaves striped crops. Check the pattern with collection trays across the swath, set the correct overlap, and keep the spinner/impeller in good condition. This tool sets the rate; pattern testing is a separate, complementary check.
Can I calibrate a manure or lime spreader the same way?+
Yes — the strip test works for any broadcast material: granular fertilizer, lime, gypsum or solid manure. Just weigh what's applied over the measured strip. Denser or lumpier materials especially need calibration because chart settings are least reliable for them.
How often should I re-calibrate?+
At the start of each season, whenever you change product (different density/granule size), and after any repair or wear to the metering parts. A quick re-check each time protects both your fertilizer budget and your yield.
What if my rate is far off target?+
Large errors usually mean the gate setting is wrong for the product or the machine is worn or partially blocked. Reset toward the chart value for that product, clear any blockage, re-test, and adjust in small steps. The tool's % of target tells you how big a change you need.