In the Garden > Gardening Tips, Books, Techniques and Tools
Soil is the most important gardening basic there is, so it pays to get it right. Here are Don’s tips on working out what kind of soil you have, how to test the pH of your soil and how to keep your soil healthy.
There’s a simple test you can do to determine the texture, or mineral fraction present in your soil. First, dig up some soil. Now wet it. Grab a handful and scrunch it up in your palm. If you end up with a firm sausage shape that you can bend into a circle, that’s clay soil. If the soil barely forms any shape and just crumbles, that’s sandy soil. And if the soil holds together but can’t be bent without cracking, you have a loam.
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.
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.
Sandy soils don’t retain moisture and they are low in nutrients. On the plus side, they are well aerated and they’re loose and easy to cultivate. They are often classed as ‘poor’ or ‘coarse’ soils.
The term 'loam' covers all the soils between sandy soils and clay soils. While a loam is said to be the perfect soil for growing plants, in many areas of Australia it is unlikely that you would find a 'true loam', halfway between a sandy soil and a clay soil. Some loams will have propertiessimilar to sandy soil, while others will be closer to clay soil. Whatever type of loam you have, you can improve it and keep it healthy by adding organic matter, such as compost, mulch and manures.
Some plants like to grow in acid soil, others prefer alkaline soil, and many others aren’t so fussy. For instance, if you put lavenders into a highly acid soil they don’t do all that well; Japanese maples also like an alkaline soil. When soil pH is right for a plant, it will absorb nutrients from the soil because all the conditions for the various chemical reactions are OK. When soil pH is wrong for a plant, it simply won’t absorb nutrients, even if its roots are surrounded by nutrients.
If you don’t want to buy a soil test kit and test the soil yourself, your local nursery can test a soil sample for you (but talk to them first about it, to find out what they need). It’s much better (and very easy) to test your soil yourself. This is useful, as soil pH can vary from one part of your property to the next (say, front garden and rear garden). There are several different soil pH test kits available.
Your local nursery can give you expert advice on this – what to add and how much, etc. Adding lime and dolomite to soil raises its pH. Adding iron sulfate to soil can lower its pH. An alternative is simply to leave the soil pH as it is, and only use plants that can cope with your soil’s pH level. Here are some examples of plants that tolerate acid soil, and plants that tolerate alkaline soil:
‘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@example.com or phone (03) 9662 7666 in Melbourne, or 1800 645 051.
An article titled ‘All About Soil’ is featured in the April edition of the Burke’s Backyard Magazine. The magazine is available at newsagents and supermarkets for $5.50.
Copyright CTC Productions 2003