Methodology

Product data

• Each of the 302 products has a published analysis taken from a manufacturer or brand source, linked on the product page with the date we checked it.
• Sources are manufacturer and brand product pages and brochures (including PDF product guides) that we fetched and read. Where a brochure lists a product on its own list we say so in the product note. Some manufacturers’ sites block automated reading; we did not list products from those.
• The nitrogen comparison and the “Find my fertiliser” ranking rate only the products whose nitrogen form we have verified, not the whole directory. Everything else is listed for its published analysis. Check with your agronomist before choosing a product.
• A value we cannot read from a source stays blank (shown as “—”). We do not estimate or copy a typical value.
• Analysis percentages are as published, which for some products (for example liquids) may be weight/volume rather than weight/weight. Product pages say so where we know.
• Outbound “buy” links go to manufacturer or brand pages only, were checked for a working page on 17 October 2026, and are not affiliate links.

Prices

We hold no price feed. The only prices on the site are third-party asking prices for bulk urea and sulphate of ammonia read from one public listing page on 17 October 2026. They are ex GST, have no listing date, exclude freight and spreading, and are labelled indicative everywhere they appear. They are not quotes. Where we have no verified price, the site says so and the calculators leave the field for you to fill in.

How recommendations work

“Find my fertiliser” ranks nitrogen products for your crop, soil, pH and application method using a published rule and no commercial input:

1. It estimates the share of nitrogen lost to the air as ammonia for each product, using ranges from published Australian studies (listed below), adjusted for soil texture, pH and whether the product is incorporated.
2. It adds a penalty where a nitrate form could leach on sandy soil, and a small penalty for products that need specialist equipment.
3. It adds a small tie-breaker favouring more N per tonne, because there is less to cart and spread.
4. Lower totals rank higher. If you enter your own prices for all of the top three, those three are re-ordered by effective cost per kg of N after losses.

Where a loss figure is our assumption rather than a published number, the comparison tool marks it as unverified. The estimates are for planning, and the results page says so.

Sponsors and independence

The recommendation engine does not read sponsor data and cannot be influenced by it. A sponsored slot exists in the code but is switched off. If it is ever enabled it will be labelled “Sponsored”, kept separate from recommendations, and linked to a verified page.

Articles and guides

• Every number in a guide links to a source or is marked as arithmetic, with the assumptions written out.
• Each guide has a “What we could not verify” section. If we could not confirm a figure we leave it out or flag it.
• Guides are written by the Fert Directory editorial team. They are not yet reviewed by a qualified agronomist, and say so on the page. We currently have 6 guides.
• Each guide shows when it was published and last updated.

Sources

15 references are held in our data, 11 of them marked “verified” (we loaded the page and read the relevant passage on 17 October 2026) and the rest “partly verified” with a note. The full list, with the claims we use from each, is on the comparison tool page. Several sources are historic or published by a manufacturer, which is flagged.

Corrections

If you spot an error, tell us. We correct verified mistakes, update the “checked” date, and note material changes to articles. We do not remove criticism of the site.

For developers and AI assistants

The same data is available as JSON at /api/v1/products, and a plain-text summary is at /llms.txt. Please keep the sources, dates and the disclaimer “Always check with your agronomist before acting” with any figure you reuse, and do not present indicative prices as quotes.

Limits

Loss ranges come from few Australian field measurements. Nitrogen loss is one of several pathways. Crop-by-crop product suitability is not verified. See the terms and always check with your agronomist before acting.