May 17th, 2023 by Shauna Hammond

Lawn fertiliser is one of the most common ways to keep your lawn healthy and ensure that it is getting all its required nutrients. If you have a green thumb, it's easy to get excited about the prospect of adding some nice, healthy fertiliser to your yard. But there are a few things that can trip up even experienced gardeners who aren't aware of all the facts about lawn fertiliser and if you are just starting out then it can all seem a little bit confusing. This will help you understand what makes one type different from another, how much is too much, and what type of fertiliser is best for your particular situation.

What is the purpose of lawn fertiliser?

Let’s start from the very beginning and explain what exactly fertiliser is - the main purpose of lawn fertiliser is to help plants and lawns. Fertilisers can be organic or inorganic, but both serve the same purpose: to provide the necessary nutrients that plants need to thrive. Organic fertilisers include compost, manure, and bone meal. Inorganic fertilisers are man-made products that contain various minerals and other ingredients that serve as nutrients for your grass (and other types of vegetation).

Lawn fertiliser is an important part of maintaining a healthy lawn. It can help to improve the appearance, colour and density of your grass, as well as encourage it to grow thicker and faster. However, there are many different types of fertiliser available and it's important that you choose one which suits your needs. For example: organic or chemical? Spring or fall application? How much should I use?

Types of fertilisers

As mentioned most fertiliser fall into two main categories – organic and inorganic but these can then be further split into slow-release and fast-release, so let’s get to know these fertiliser types a bit better.

Organic fertilisers

These fertilisers are made up of organic matter such as manure and compost that can be used as food for your soil microbes--and thus help improve its health overall! Some people prefer these as they are a natural source of nutrients.

Inorganic Fertilisers

These are also known as synthetic or chemical fertilisers and are manufactured products that are typically derived from non-living sources and do not contain organic matter. These are primarily made up of Nitrogen, Phosphorus and Potassium – we will discuss these in more detail later on.

Slow-release

As the name suggests these fertilisers release nutrients slowly over time, which means you only have to apply them a few times of year. They're best for maintaining healthy grass growth in the long term and for use on soil types that do not hold nutrients as well such as sandy or silt soil as they will continue to release nutrients over a longer period of time giving plants more opportunity to absorb them. Slow-release fertilisers are best for the environment because they don't leach as much nitrogen into nearby rivers or lakes, which can lead to algae blooms that kill fish and other marine life

Fast-release

fertilisers release their nutrients more quickly than slow-release ones do, so they are better for lawns that need an immediate burst of nutrients such as helping your lawn recover after it's been damaged by pests or diseases.

What are the NPK levels and what do they mean?

As mentioned above NPK stands for nitrogen, phosphorus and potassium, these are the main ingredients in most inorganic fertilisers – these nutrients are the primary ones needed by plants and grass in order to grow strong and healthy. NPK level is the standard measurement used to describe the amount of these three nutrients in a fertiliser. The NPK levels are listed as a percentage of the total amount of nutrients in the fertiliser (for example, 5-10-5). This makes it easier to select the right fertiliser for your plant and lawn needs. So, what do these nutrients do?

Nitrogen - is required by plants during growth periods (spring and summer) when leaves are produced or grown larger it encourages leafy foliage and is also important for the production of chlorophyll which give grass and plants their vibrant green colour.  

Phosphorus – This is very important for helping with root development and flower production, this nutrient is particularly important for freshly seeded plants and turf.

Potassium - Promotes cell division and strengthens stems, it also makes plants and grass hardier so they can better combat lawn disease, drought and cold.

These nutrients will sometimes be paired with other nutrients such as magnesium or iron which will help these nutrients to perform even better and have added benefits usually of helping with the production of chlorophyll to make grass greener.

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How can I make sure my lawn gets just the right amount of nutrients?

To ensure that your lawn gets just the right amount of nutrients, you should test your soil and use the right kind of fertiliser at the proper time. The best way to test your soil is through analysis with a home testing kit. These kits are inexpensive and easy to use; they will tell you exactly what nutrients are lacking in your soil so that you can buy fertilisers tailored specifically for those deficiencies. If you're worried about doing this yourself (or don't have access), ask around among friends: many people have done it before and may be able to help out! It is important that you adjust your fertiliser to suit your lawn’s changing needs, there is no one size fits all fix and different seasons, climates and different stages of the growth cycle will affect what nutrients you need to prioritise.

We hope that you now have a better understanding of fertiliser and how it can help your lawn and plants, and a better understanding of NPK levels and what they contribute. It is important to ensure that you are always adjusting your fertiliser to your garden’s current needs.