Soil Preparation for Instant Turf

Date Posted: 10 September 2017 

Soil preparation is by far the most important step in your instant turf project. Good preparation will provide the foundation your lawn needs to become the hard wearing, drought tolerant surface that you’re looking for. When it comes to giving advice aro Soil preparation is by far the most important step in your instant turf project. Good preparation will provide the foundation your lawn needs to become the hard wearing, drought tolerant surface that you’re looking for. When it comes to giving advice aro

Soil preparation is by far the most important step in your instant turf project.  Good preparation will provide the foundation your lawn needs to become the hard wearing, drought tolerant surface that you’re looking for. When it comes to giving advice around soil preparation, we get lots of questions on this like:

  • How do I know if my soil is good to lay lawn on?
  • How much soil should I remove / how thick a layer of topsoil should I bring in?
  • What sort of top soil should I buy?

So let’s go ahead and answer each one of these.

How do I know if my soil is good to lay lawn on?

South Australia has a very diverse mix of naturally occurring soil types ranging coarse sands to heavy clays. I once had a property that had naturally occurring deep white sand in the front yard and hard setting silty clay in the back yard. Because of this diversity, it’s hard to come up with a “one size fits all” approach to preparing your soil for lawn. I often say to customers that there are 2 soil characteristics that lawns don’t particularly like. Those are: soils that set hard and soils that repel water (non-wetting soils). Both of these characteristics limit the lawns ability to develop deep roots and they both have implications on how able the soil is to accept and drain water.

Non wetting soils tend to be sandy in nature and can be treated with a wetting agent. As a general rule,  non wetting soils can only be treated.  They can rarely be fixed so that they permanently no longer repel water. This is because wetting agents can only temporarily treat the non-wetting nature of the soil. Eventually the wetting agent will break down and the soil will become non wetting again. Non-wetting soils are one of the largest issues for lawns. Because the soil repels water, the lawn does not develop deep roots and therefore becomes weak and susceptible to an array of issues.  Hard setting soils are not as much an issue as non wetting soils but are none the less not good for lawns. These soils typically include clay types. They are boggy in winter and are dry and super hard in summer.  Lawns don’t like being water logged and they don’t like hard soils because it limits their ability to develop deep roots.  If you have either of these characteristics present in your soil, you will need to do some preparation prior to laying turf.

What lawns do like is freely draining, structured, pH neutral (7) soils that don’t set too hard. If you If you think that this is you then your soil is probably good to lay turf on. Even if you have good soil, at the very least you will need to turn it over and maybe add a thin layer of sandy loam to help you level it out.  If you want some advice on your soil, bring down a sample to our store at Hove, SA and we’ll analyse it for you free of charge.

How much soil should I remove / how thick a layer of topsoil should I bring in?

This is a tricky question to answer! It all depends on how good your top soil is. If you have issues similar to those mentioned above, the safe option is to remove a 100mm layer and replace it with sandy loam. This is an expensive exercise and should only be done if your top soil is poor. Other options include removing a 50mm layer, applying and rotary hoeing in a 25mm layer of sandy loam, then finishing the surface off with another lighter layer of sandy loam to smooth the surface off and make it easier to level.

What sort of top soil should I buy?

This is a question that can be answered in many different ways – lots of people have an opinion on it so I’ll tell you what we do and what works for us.  Our turf is grown down in Langhorne creek, south of Adelaide. It grows on a soil made up of nearly 80% sand, the rest being silt, loam and clay. You can buy this type of soil in most landscape supply yards and it’s called Sandy Loam. If you have the means, there are other types of sandy loam around with added composts and manures which are helpful when establishing a lawn. These additives help to temporarily hold water and nutrients in the soil which in turn help the turf establish faster, with less stress.  You’ll have success with which ever you use.  One thing I can say is that you generally get what you pay for. Some of the cheaper ones can set hard and can be non wetting which are ironically the two things you are trying to avoid when preparing soil for a new lawn.

To finish a soil off, your surface should be compacted, levelled and screeded till perfectly flat. Make sure you allow a 25mm gap between the finished soil height and the top of your lawn edge to allow room for the thickness of the turf roll.


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