Almost every fertiliser cost comparison you will read online is built on invented numbers. We are not going to do that. Here is the method instead, and a calculator that uses your figures rather than ours.
The single most common error is comparing price per bag. A bag is not a unit of anything useful — products differ in application rate, nutrient concentration and how much survives to reach the plant. Two products at the same bag price can differ substantially in cost per hectare.
The second error is stopping at input cost. The number that matters commercially is cost per tonne harvested, which means yield belongs in the calculation. We have no verified yield trial figures to publish, so we will not put a percentage in front of you — that is exactly the kind of claim that should come from a trial on your own land.
So this page gives you the method and an honest calculator. Both sides of the comparison use numbers you supply: your current programme from your own invoice, and our quote for yours.
| Factor | What it tells you | How to treat it |
|---|---|---|
| Price per bag | Tells you almost nothing on its own | Ignore it as a comparison basis |
| Rate per hectare | Rate × price gives cost per hectare | This is the minimum honest comparison |
| Nutrient concentration | Differs between products | Compare cost per unit of nutrient delivered where relevant |
| Leaching loss | Varies with soil, rainfall and product solubility | Affects how much you actually paid per nutrient reaching the plant |
| Application labour | Differs by rate, form and number of rounds | Include if rounds differ between programmes |
| Transport | Varies with volume and delivery location | Ask for delivered pricing, not ex-works |
| Yield response | Crop, soil and season specific | Establish on your own trial block — we publish no yield claims |
| Cost per tonne harvested | Input cost ÷ yield | The number that actually matters, and only a trial gives it to you |
Use the cost-per-hectare calculator with your own invoice figures and our quote. It models partial substitution, because that is how most growers actually start. It deliberately excludes yield, because we will not put an invented percentage into your business case.
The only comparison that binds is the one from your own soil. We will design a trial against a control block and review the result with you.
Model both programmes with your own figures, including partial substitution.
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