Fertilizer Spreader Calibration & Hit the Right kg/ha

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.