What does NPK mean?
Quick answer
NPK stands for nitrogen (N), phosphorus (P) and potassium (K), the three main nutrients in fertiliser. A fertiliser's analysis lists how much of each it contains, as percentages. Nitrogen drives leaf growth and colour, phosphorus supports roots, and potassium helps the plant cope with stress. Compare products by their analysis, not just the brand.
Why this happens
Every fertiliser label includes an analysis: a list of the nutrients in the product and how much of each, as a percentage. The three main ones are always listed first, and they’re what “NPK” refers to:
- N, nitrogen: the nutrient lawns use most. It drives leaf growth and green colour. Too much causes soft, fast growth and more mowing.
- P, phosphorus: important for roots and establishment, which is why it features in fertilisers for new lawns.
- K, potassium: helps the plant regulate water and cope with stress such as heat, drought and wear.
Labels also list other nutrients, such as sulfur, iron, magnesium and trace elements, and sometimes how much of the nitrogen is slow-release.
Reading the numbers
If a granular fertiliser lists nitrogen at 20%, then 1 kg of product contains 200 g of nitrogen. The label rate then tells you how much product goes on each square metre, so between them you know how much nitrogen your lawn receives. The Lawn Journal does this sum for you when you log an application of a product whose analysis we have on file.
Choosing by analysis
Lawn fertilisers are usually higher in nitrogen than in phosphorus. A soil test is the best way to know whether your lawn needs more of a particular nutrient. Without one, choose a product made for lawns, at the label rate, and watch how the lawn responds.
Why you can’t just add more
Nitrogen doesn’t stay in the soil for long. What the grass doesn’t take up can leach below the roots or wash off in heavy rain. That’s why the label rate and timing matter more than the strength of the product: smaller, well-timed feeds in the growing season do more for the lawn than one large dose.
What you can do
Find the analysis on the labelCheck first
It's usually a panel listing nutrients and their percentages.
Compare per application
A product with more nitrogen per kilogram may be applied at a lower rate. Use the label rate to compare what actually goes on your lawn.
Track what you've applied
Your Lawn Journal can add up the nutrients you've applied this year from logged products with a known analysis.
What not to do
- Assuming a higher nitrogen number is always better. More nitrogen means more growth and more mowing, and too much at once can burn.
- Ignoring the rate. The analysis and the rate together decide how much nutrient goes on.
How much do I need?
A label rate of "20 mL per 100 m²" means: Rate 20, mL, per 100 m². Per hectare? Use 10,000 m².
How much you need
Enter your lawn area and a rate to see how much product and water you need.
What's next
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Sources
- Understanding pesticide chemical labels (booklet), Australian Pesticides and Veterinary Medicines Authority (APVMA)Reading product labels. Accessed 4 October 2026.