Many soil types that have a high clay or silt component will cause ongoing water logging and drainage issues for a new St Augustine lawn being grown in these conditions. St Augustine lawns with drainage issues can be weak and prone to easy and ongoing damage, be prone to weeds, pests, diseases and moss, and be constantly ugly and unsightly.
So for these heavy clay or silt based soils, the homeowner must realise that without undertaking major soil improvement before the new St Augustine sod is laid, the lawn will suffer many problems throughout its entire lifespan.
This is a judgement call for the homeowner to make as to whether this is necessary for their property or not. Having made that decision, then we must fix that soil, BEFORE the new St Augustine grass is laid.
In some cases, some St Augustine lawn owners will already have an existing lawn which has experienced exactly the same water logging issues and may be needing to be removed and replaced with new sod.
Improving Existing Soil
Our first option is to improve the existing soil on our properties by adding supplements to the soil which will greatly aid in water drainage and increase the free flow of water throughout the soil.
This should be done on soils with only minor or medium levels of water logging concern, and this will need to be a judgement call on behalf of the homeowners themselves.
We have two options to improve soil drainage in these conditions.
Both options involve adding either coarse sand or sandy loam substantially to the existing soil, and then using a rotary hoe to mix and blend the two soil types together as much as possible.
Blending coarse sand into the existing soil is the first option. This should be done when the soil is of high quality, and may naturally contain high levels of organic matter. So a straight out inert coarse sand will increase the drainage of these soils best. While at the same time decreasing the level of organic matter in the soil which may create issues with many lawn pest invasions, as well as a lawn which grows too fast and requires too much work to maintain.
The soil is still rich enough to easily maintain a healthy lawn, and now has the greatest repair done for drainage problems.
Blending sandy loam is our second option, and is best suited to existing soils which may already be low in nutrition or existing organic matter. Sandy loam is a wonderful base for most lawn types, and as such would be a good choice to improve these soil types to create much greater drainage, and reduce water logging issues from arising in the future.
Replacing Existing Soil
For the worst affected soil types which have the worst drainage problems of all, then our best course of action will be to totally replace the top soil where the new St Augustine lawn is to be planted.
Once again, whether or not to do this will be the judgement call on behalf of the homeowner themselves, and we cannot advize whether this is right for your property or not.
The existing heavy clay or silt based soil will need to be removed to a depth of between 8 to 12 inches, and disposed of, this would best be undertaken by use of a small soil digging machine, or to call a professional to do the job for us, because its a very big job with a lot of waste matter to be disposed of, or used or improved for another area of the property.
The top layer of soil would then be equally replaced with sandy loam which is available from our local soil and garden suppliers. Sandy loam is one of the best known soil types for laying of new turf, and would thus be our first option. We should be sure not to replace this soil with a soil which has a lot of organic matter for the main reason that it can encourage many lawn pests, and excessive growth rates.
The replacement of this top soil for the new St Augustine turf will allow for the healthy development of the majority of the roots of the lawn with lots of oxygen and no water logging. The same depth will also ensure the greatest possible chance of removing any water logging occurring on top of the St Augustine grass as well. And lastly, if the lawn is being grown on a slight slope, then much of this excess water will also be drained away to the lowest point of the lawn within this same topsoil profile where the lawn is growing in the sandy loam.
Soil Compaction Before Laying New St Augustine Grass
After either soil improvement has been undertaken, the soil will need to be compacted prior to the laying of any new St Augustine turf. This is vitally important for two reasons.
Firstly is so that the lawn be properly laid on an even soil bed, with far less chance of the lawn developing sloping and grooves as the soil slowly compacts on its own over the years.
And secondly is that for soils which aren't properly compacted prior to new roll on sod being laid on top, there is just far too much oxygen in and around the roots of the turf as it is trying to establish itself, and new lawns laid in such conditions do very poorly, and can even die off in areas.
So be sure to properly compact and level all soil improvements prior to laying of new St Augustine grass turf.