Clay Soils
Many people think that the worst soil you can have in the garden is heavy clay. However, Don explained that any soil can be a good garden soil. Indeed, most natural soils in Australia are suitable for growing a garden. In most instances it is better to improve your existing soil than to add bought soil to your garden.
Properties of clay soil
Clay soil is made up of millions of tiny particles, giving it a very fine texture. This has advantages and disadvantages. On the plus side, clay soils are rich in nutrients (the particles provide multiple surfaces where nutrients can ‘stick’) and they hold water well. However, they are also prone to compaction, waterlogging, and can be sticky when wet and tough when dry. These problems are made worse if a clay soil is cultivated when wet.
Improving clay soils
The best way to improve clay soils is to add organic matter such as well-rotted manures, mulch and compost. This binds the particles together, improves the soil structure and allows water and oxygen to move through the soil more easily. Adding sand to clay soils may help improve drainage and aeration, but you would need to dig in huge quantities to have any real effect. The addition of gypsum (often sold as claybreaker) or lime can also be beneficial and again this can be dug through the soil. It is important only to cultivate fine-textured soils when they are ‘damp-dry’, not when they are wet.
Further reading
‘Gardening Down-Under – A Guide to Healthier Soils and Plants’ by Kevin Handreck (Landlinks Press, $39.95, ISBN 0643066772). Available from major book stores or mail-order from CSIRO Publishing, PO Box 1139, Collingwood, Vic, 3066, on the web at www.publish.csiro.au, via email at [email protected] or phone (03) 9662 7666 in Melbourne, or 1800 645 051 (Freecall within Australia).