The dirt on Sandy Loam

What type of topsoil is the right type when it comes to preparing your area for turf? - it's a question everyone will ask themselves when thinking about putting a new lawn in.

Good soil preparation when installing turf 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 about soil preparation,  we get lots of questions on this, such as

• How do you know if your existing soil is good enough to lay turf on?

• How much soil do you need, and what is the best type?

South Australia has a very diverse mix of naturally occurring soil types ranging from coarse sands to heavy clays. I once owned 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, there isn't a “one size fits all” approach to preparing your soil for lawn; however, there is an underlying principle that applies to all circumstances., that being: Lawns grow best when they have at least 100mm of good quality top soil under them. When I say good quality, that means soil that doesn't set hard, accepts and holds water and is commonly a combination of sand, loam and organic material.

There are often times when the existing soil on your property is perfectly fine to lay turf on. There are also times when it is not OK, so it's worthwhile investing some time in understanding how good or not your soil is. I often say to customers that there are some soil characteristics that lawns don’t particularly like. Those are;

• Soils that set hard
• Soils that repel water (non-wetting soils).
• Soils that are rocky or shallow

These characteristics limit the lawn's ability to develop deep roots and have implications on how able the soil is to accept and drain water.  The best way to investigate your soil is to dig out a core sample using a hand trowel or spade. Take notice of how difficult it is to dig the core. If the soil is compacted or shallow, this won't be an easy job. Once you have the core sample out, slowly pour some water on it from a cup and note how well it absorbs and holds water.  While you're there,  have a look at the soil itself.  Is it rocky, shallow, or made up of heavy clay? All these factors go into the decision-making process of whether to use your existing soil or replace some of it. If you're soil exhibits some poor characteristics, you’ll need to replace some of it with some fresh topsoil. 

The best top-soil to use:

When it comes to topsoil for lawns, most people recommend sandy loam. Sandy loam is just as the name suggests – a mixture of sand and loam. The percentage of each of these can vary, but the most common mix is 80% sand and 20% loam. Some landscape yards mix in compost and manures, and others just supply straight sandy loam.  Lots of people have an opinion on which type of sandy loam is the best, so the best way to advise you is to tell you what we do and what works for us.  Our turf is grown down in Langhorne creek, south of Adelaide. It grows on soil made up of nearly 80% sand, the rest being silt, loam and clay, and I can say that the turf loves it. Being primarily sandy in nature, it doesn’t hold water for long periods of time, but it does allow the roots of the lawn to grow down deep, which is what you want. In this way, sandy loam is ideal and the correct soil to use when preparing an area for turf.

If you would like your soil to hold more water, there are options. You can buy sandy loam products 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 helps the turf establish faster, with less stress. 

You’ll have success with whichever of these types of sandy loam you use; however, I can say that, as with most things in life, you generally get what you pay for. Some of the cheaper Sandy Loam products 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, so make sure you ask the landscape supply yard some questions about these sorts of things.

How much should you apply?

The depth of the layer that you should apply will depend on a few factors related to the quality of the existing topsoil on the site. The most you'll need is a 100mm layer; however, there are often times when you'll need less.  If you would like to get an opinion on your soil and how much topsoil you may need,  bring a sample down to us at our store in Hove, and we'll let you know what (if anything) needs to be done.

Click here to read some handy tips and advice on the process of preparing your soil ready for instant turf. If you find that you have some questions that we don't cover, give us a call on 08 8298 0555 or send an email to me at stefan@paulmunnsinstantlawn.com.au