Guide to Soil Amendment and Nutrition Management

Search for lawn fertilisers, and you will find hundreds of options with different numbers and words in the description. It is hard to figure out which one to buy if you do not know what it all means. To make things more complicated, if your soil is not in balance, even the best fertiliser may perform poorly.

This guide explains in detail how to get your soil in balance, from understanding your amendment requirements, through to choosing the right fertiliser with the NPK ratio, to applying your fertiliser correctly.

Identifying Amendment Requirements

Lawn grasses obtain thirteen of their sixteen essential nutrients from the soil via the root system. Therefore, a soil test is the best way to determine the nutrient status of the soil and determine whether more of a particular nutrient is needed for optimum lawn growth.

When you are trying to have a lush green lawn, you need to know the following things about what is going on in your soil. These indicators can be identified from a good soil test:

  • pH.
  • Exchange Capacity (EC) the ability of the soil to retain and exchange nutrients.
  • organic matter percent (humus), a critical component of soil structure.
  • major cations and anions (Ca, Mg, K, Na), Phosphorus and essential minor nutrition determination.

The Lawn Pride soil test is the turf specific soil test that offers the best way to determine the level of specific soil nutritional components that are required to be assessed for maintaining lawn. This test is most suited to analysing lawn soils and is designed to be applicable across a wide range of soil types.

Soil Amendments

Organic matter

is a critical component of good soil structure. Organic matter improves the water holding capacity of the soil, creating exchange sites for nutrients and water. Hence, it is desirable to measure the organic matter levels in a soil profile, and to maintain the soil’s ability to retain and exchange nutrient cations through the programmed addition of organic materials.

If your soil test identifies the need to improve the soil's exchange capacity, the application of amendments such as LawnPride Hydramaxx can improve the soil’s ability to retain and exchange nutrients.


Calcium is the most important cation for lawn growth and maintenance. This is highlighted by its many functions in the soil and plant, the most important being to displace and leach the destructive cation Sodium and in turn maintain good soil structure.

Appropriate Calcium amendments, such as Lime or Gypsum, would therefore be applied in an on-going program to maintain the concentrations of both nutrients to sufficient levels required for lawn.

Optimum lawn growth is achieved on soils with adequate pore space, which provides air and water and space for the root system. Soils with high Calcium content have good structure because particles cling together, or aggregate, providing pore space.

How to Read Lawn Fertiliser Numbers

On any lawn fertiliser label, you will find a combination of three numbers. They might be 21-1-9, 18-10-10, 16-4-8, or any other combination. Those numbers are called the NPK ratio. The NPK ratio is the most important factor in choosing the right fertiliser for your lawn.

NPK stands for nitrogen (N), phosphorus (P), and potassium (K). These are the three most important nutrients for your grass. The numbers in the ratio tell you what percentage of each nutrient the fertiliser contains. For example, a fertiliser with an NPK of 10-10-10 is 10% nitrogen, 10% phosphorus, and 10% potassium.

Nitrogen, phosphorus, and potassium all serve a different purpose:

  • Nitrogen boosts fast growth and dark green colour.
  • Phosphorus encourages strong root growth.
  • Potassium improves disease resistance and overall plant health.

The following application ratios have been developed utilising the Nitrogen (N) to Potassium (K) ratios of the Lawn Pride Controlled Release (CRN) fertilisers.

The N to K ratio simply refers to the relative relationship between these two primary nutrients, rather than the specific number of kilograms of each in a fertiliser blend.

High Nitrogen Ratio – apply high Nitrogen to Potassium ratio fertilisers (2:1 or higher) when:

  • The lawn to be fertilised is in overall good condition.
  • The desired result is consistent and/or accelerated top growth.
  • Applying in spring when no fertiliser was applied in winter.

Balanced Ratios – apply 1:1 Nitrogen to Potassium ratios when:

  • Lawn is in good condition and general maintenance is desired
  • Stressful periods such as high traffic and wear situations
  • A reduction in top growth is desired

What to do when

Whilst the seasons do differ around Australia, as a general rule, the table below is a good reference guide for you soil testing, soil amendment, and nutrition planning for your lawn.

Month Activity Comments
May - Jun Soil Test Use a turf specific test for best results
Jun - Aug Apply amendments Based on findings from your soil test
Sep - Dec Apply a CRN (N to K ratio 2:1) such as Maintain If renovating, use Groturf as the extra phosphorous will help your lawn's recovery.
Apply a CRN (N to K ratio 2:1) such as Maintain
Supported by the LawnPride Liquid range
May Apply a CRN (N to K ratio 2:1) such as Turfmaxx Fertiliser to sustain your lawn through winter


Controlled Release Nitrogen Fertilisers

Nutrition programs implemented by Lawn enthusiasts over recent years have seen a move away from agricultural instant release fertilisers to superior controlled release nitrogen (CRN) fertilisers.

Agricultural fertilisers used on an ad-hoc basis, result in an over-abundance of nutrient during the initial fourteen days after application without the longevity required to sustain optimal growth patterns. This type of process results in accelerated lawn growth, causing excessive clippings and weak lawn that is susceptible to pest and disease damage. Once nutrients are exhausted and reapplication does not occur when required, weakened lawn develops.

The use of a controlled release Nitrogen (CRN) source has proven to be a cost-effective strategy to optimise soil nutrition without the need for fertiliser applications every four to six weeks during the growing season. In sand profiles, where nutrients are more difficult to retain, the result is leaching of nutrients out of the reach of the lawn, often into areas where they are not needed or wanted.

With a wide variety of technologies available at an affordable cost, the use of CRN fertilisers has become prevalent within Australia. Lawn Pride has a range of product choices with varying NPK ratios, particle sizes and particles coated allows far greater fertiliser efficiency over differing lawn growing regimes and conditions. CRN fertilisers will control the release of Nitrogen for up to twelve weeks maintaining growth habit and reducing mowing frequency, clippings, and pest & disease problems.

Liquid Fertilisers

Liquid fertilisers will provide a quick response from your lawn. The nutrients are almost immediately available to be absorbed through the roots or leaves, correcting nutrient deficiencies quickly or giving the plant a general boost through the growing season.

Using liquid fertilisers does not mean you do not have to apply a granular CRN fertiliser, the liquid products in the Lawn Pride range are designed to correct deficiencies, stimulate root growth, and the general health and presentation of your lawn.

Lawn Care Programs

As you can see, getting the best out of your lawn requires a few important steps that once followed, give you great results. To ensure you get the best from your lawn, Lawn Pride have developed a range of Lawn Care Programs for the popular turf varieties commonly used for Aussie lawns.

You can also contact our support team at where we can answer your questions and help you to have the best lawn in the street!