How to check your soil health

Scotch College, Grounds and Horticulture Manager

Peter Harfield

Adelaide, South Australia

Is your lawn thriving or failing? Now is the perfect time to look below the surface to see exactly what’s going on. A simple soil test can unlock all the answers to improve your lawn.

Over his four decades of greenkeeping, Peter Harfield, Grounds & Horticulture Manager at Scotch College Adelaide has honed the art of growing grass, but he still brings it back to basics with regular soil tests on the lawns he manages. He’s one of the industry leaders John Deere is partnering with this season to discover the secrets to a lush, healthy lawn.

This test simply involves digging a small hole to examine root growth and soil structure. It’s a tried and true trick with the power to transform grass for any lawn lover.

“The key to a healthy lawn actually lies beneath the surface.”

Peter’s soil testing tips for creating a lush, healthy lawn.

Soil health: why it’s important for a good lawn

Many people do not realise roots need room to breathe – their growth revolves around the aeration of the soil. All lawns need healthy, aerated soil to encourage roots to spread and flourish, which will create a great leaf on the surface.

Deeper healthy root systems make it easier for grasses to endure environmental stressors, such as hot and dry periods.

How can I check if my soil is healthy?

There is no substitute to digging a hole and having a look at the soil for yourself. Even professionals can forget to perform this basic task. No one has X-Ray vision, so if you don’t look below the surface at your soil you are simply guessing.

How can a soil check be performed at home?

All you need is a little spade. Dig a small, square hole 100–150 mm deep. From there, you can closely examine the sample you have retrieved.

What should we be looking for in our sample?

Firstly, check to see how moist the soil is. If it looks and feels old and dry, you will know it needs watering, some aeration, and wetting agents to rehydrate the root zone area as soon as possible.

You can also check to see how deep the roots are growing, and if they are doing what we want them to do and are chasing water deep underground. If it’s in good health, your sample will have visible, white coloured thriving roots throughout the square.

What does a healthy soil sample look like?

The ideal soil sample looks like a big piece of chocolate cake – a consistent, rich colour that’s moist.

What does an unhealthy soil sample look like?

The worst kind of sample will look like a rainbow-layer cake. Layered soil has a slow water penetration rate and indicates the soil and air exchange is very slow in reaching into the root zone. When you see this, think of it like your grass is trying to run a marathon while holding its breath – it is not a good sign.

If we find out we do have a rainbow-layer cake, what should we do?

If replacing the soil with a complete makeover is not possible, the next best thing to do is physically open up the soil with something like a garden fork. To be honest, not much beats a good old garden fork being driven into the ground as the prongs help to break through the layering effect, which in turn, will speed up the water infiltration into the soil and also allow the soil gasses to easily be exchanged with the atmosphere.

What other steps can be taken to improve your lawns and moisture in soil?

You can try mixing up some molasses with water and applying it to the grass. I recommend about 20 ml of molasses for one litre of water. Molasses is carbon-rich and an efficient method to improve soil and in turn plant health.

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