Should I apply lime to my lawn?

When is the best time to apply lime to your lawn? 

No not the lime you eat, the lime we are talking about here is calcium carbonate from limestone.

A hungry lawn needs feeding but if your soil pH is not correct, it simply won’t take in what you feed it. Soil pH is a measure of acidity and alkalinity and most lawns like to be in the 6 to 7.5 range for optimum performance. Acids have a pH that is less than 7 and Alkalis have a pH that is greater than 7. Getting your soil pH in the 6 to 7.5 range is important because it influences your lawns ability for plant growth. An optimum pH will provide your lawn with better soil bacteria, nutrient uptake and soil structure. It’s a bit like your lawn has its mouth wide open and it can take up all the available food without restriction.

Most Australian soil types are acidic more-often-than-not and the process of scratching off the topsoil when you’re building can expose more highly-acidic clay and this will potentially affect your lawn in the long-term.

Test your soils pH

Measuring a soil’s pH is easy to do, all you need is a pH testing kit and they are readily available at most hardware stores and nurseries.

My soil is acidic, what should I do?

So, you have undertaken the pH test and you have found that your soil is acidic. What do you do? Well, this is where lime comes in. Lime is very alkaline, so it helps by reducing soil acidity which in turn improves the uptake of major lawn nutrients such as nitrogen, phosphorous and potassium. Dolomite lime also provides a great source of calcium and magnesium for the lawn and helps improve water penetration.

Lime treatment

If your soil is a sandy loam, acidic soils can be helped with an application of lime or dolomite at a rate of approximately 100-150 grams per square metre to increase your pH level by 1. If you have a heavier loam soil use 200 grams per square metre and 300-400 grams per square metre for heavy clay soils – it is often best to apply this amount of lime over two or three applications, with a few weeks in between to avoid causing any shock to your lawn. This will also allow you to test your pH again, so as to not over rectify the problem. As a guide, an adult hand will hold approximately 100 grams.

For an established lawn, which may be lacking magnesium, mix 50/50 lime and dolomite as the liming material to get the right balance of calcium and magnesium. Dolomite lime is also readily available as a mix and will provide favourable conditions for the formation of humus from organic soil matter. When applying lime simply broadcast it over the surface of mown grass and make sure you water it in well so that it moves into the soil. It is also recommended that you don’t fertilise your lawn within two weeks of application as you can cause burning to the grass leaf by doing so.

After the lime application, your grass will improve in colour and your lawns health will improve, providing it with a greater resistance to disease. A more robust and healthy lawn will also be much better at preventing weed infiltration.