Improving Lawn Soil
The soils underneath our lawns are more responsible for delivering good lawn health than anything else. Lawn soils provide nutrients (food), water and oxygen to the grass, and if any of these things aren't right, we simply cannot grow a strong healthy lawn.
So if we have an established lawn which isn't doing as good as it could be, then our lawn soil may be responsible. Short of removing the entire lawn and replacing the soil and laying new sod, there are some ways to improve the soil of a lawn.
Most methods will require time, different treatments and some expense as well, and improving lawn soil should be considered as an ongoing process of lawn care, rather than a once off quick fix.
Methods To Improve Lawn Soils
Although they supply vital nutrients to lawns, chemical lawn fertilisers will not improve the soil of a lawn. We include lawn fertiliser in order to dispel any myths in this regard. Fertilisers will feed the grass - but not improve soils.
Many Australian soil types will naturally repel water, other soils become water repellent over time when they are deprived of water during long hot Summers which are often affected by heavy water restrictions.
Wetting Agents will break down the water repellent waxy coating on the grains of soil, as well as opening up the top of the soil to allow more water to flow into and throughout the soil. Once water has made it into the soil, the Wetting Agents will allow the soil to hold onto the water for longer, as well as distribute the water more effectively.
Wetting Agents should be applied once a year at minimum, and perhaps 2-3 times per year for troublesome soil types.
A pH test is the easiest, quickest and least expensive place to begin to improve a lawn soil. This simple test which is available at all garden stores for a few dollars will quickly tell us whether our soil is alkaline or acidic.
Lawns require a soil pH of between 6.0 and 7.0, and ideally at 6.5 in order to flourish, so if your test returns readings outside of these parameters then adjustments will need to be made. This is a simple and inexpensive process also.
Top Dress Lawns
Lawn top dressing to improve the soil involves applying a rich organic soil mixture to the top of the turf. This type of top dressing is best done to improve sandy soil types by applying a layer of soil no greater than 1cm thick to the top of the turf. The rich organic soil is then watered into the grass. When done correctly, there should be almost no trace of the soil left on top of the grass. This process can be repeated over the years to continue to improve lawn soil.
Organic lawn fertilisers are usually based on manure products or other naturally occurring substances such as seaweed. These can be products such as Seasol and Dynamic Lifter for lawns. While organic fertilisers cannot replace chemical lawn fertilisers, they can be added a couple of times a year to help improve the organic richness of the soil. Just be sure not to mow the lawn with a catcher after applying organic fertiliser pellets… otherwise we'll be losing all that natural goodness as the lawn mower removes the nutrients we just applied, give these organic nutrients (if in pellet form) some time to break down and mow without a catcher when the next 1 to 3 lawn mowings are due.
Aerating a lawn with a proper lawn coring machine will greatly help to break up compacted lawn soils and clay soils. Coring a lawn allows more water, nutrients and oxygen to flow through the soil profile more easily.
An application of Wetting Agents and Fertiliser should be applied and watered into the lawn directly after lawn coring.
Clay soils can have the holes left in the lawn filled in with a mixture of coarse sand or sandy loam and Gypsum to help break up the clay and improve soil health.
Sandy soils, or soils of poor quality can have a richer soil or sandy loam filled into the holes after lawn coring.
Clay soils should be aerated regularly by lawn coring, as well as having an application of Gypsum applied to the turf to help break up the clay. Sand can also be applied into these coring holes to help reduce the water logging effects of the clay. A clay based lawn soil can be easily improved over time.
Ongoing Improvement of Lawn Soils
As already mentioned at the beginning of this article, improving lawn soils is an ongoing process of lawn care over the life of the turf. For lawns which suffer from any of the problems mentioned above, then the lawn owner should regularly go back and repeat the same lawn care or remedial practices over time, and keep monitoring the health of the lawn and the soil as required.