If you have ever moved into a newly built house you probably found that all the decent topsoil had been removed by contractors in the building process. What you are left with is the subsoil, which in most cases is usually clay, with the accompanying poor drainage, poor aeration, poor nutrient density and absence of organic matter.
If you are faced with subsoil, the first thing to do is get a professional soil test done in a laboratory (to locate laboratories, ask at your local garden center or check online). This will test for soil pH and nutrient and mineral densities, and will also come with specific recommendations on how to address deficiencies. Follow these recommendations carefully, and get your soil tested again a few months down the track to see if things are improving.
As well as following the laboratory’s recommendations, it is important to start introducing good quality organic matter to your soil as soon as possible. Compost or manure will help to improve the structure of your soil, encourage healthy microorganisms, and improve drainage and aeration. There are no seasonal restrictions on when you can add organic matter; just make sure your soil isn’t too wet. Check soil tilth by squeezing a handful and watching its behavior as it crumbles. If it falls apart well, it has good workability, but if it stays solid you will have to let it dry out. If it runs through your fingers it is lacking moisture.
Organic mulch and compost should be spread to a depth of about three inches and then worked into your soil to about 8 inches, but if you are planting perennials, increase the amount of mulch and dig deeper to about 12 inches. Try to keep off the garden beds to avoid unnecessary compaction, which undermines drainage and aeration.
It will usually take a number of years for soil to build up quality, so be patient. Just keep adding mulch and compost every year and plant crops that will help fix your soil to avoid runoff and wind erosion of your developing topsoil.