In your backyard

Different soil properties may impact on the things you can grow in your backyard. The following are some properties and simple tests you can do to find out what type of soil you have.  

Soil texture

Take a handful of soil from various locations in your garden.

Wet each soil sample gradually and work it in your hand until it forms a ball. The moisture content should be just drier than the point at which the soil sticks to your fingers. Add some dry soil if the sample becomes too sticky.

Slowly squeeze the soil out between your thumb and forefinger to form a sausage-like ribbon and check:

• If it is a firm shape that bends like plasticine, it is a clay soil. These soils are usually rich in nutrients and hold water well.
• If you can see and feel sand particles and the soil crumbles, it is sandy soil. Sandy soils have low moisture and nutrient holding capacity.
• If it holds together but is still slightly crumbly, it is a loam soil. Loams are said to be the best for growing plants. Loam covers all soils between sandy and clay soils.

It may be useful to discuss the texture of your soil with your local garden centre or nursery. They should be able to provide advice about what type of plants you can grow or what you can do to improve the quality of your soil. 

Soil organic matter

Organic matter includes compost, manure and organic mulch products.

Whatever your soil type, adding more organic matter can help improve the soil structure and increase its ability to store moisture and nutrients.

Regularly adding more organic matter is recommended because high rainfall and high temperatures cause it to break down quickly.

A layer of organic mulch placed over the soil is a useful addition in garden beds. Mulch helps reduce evaporation from the soil and insulates plant roots against extremes of heat and cold. It also helps prevent weed growth. Over time, organic mulches decompose into the soil, adding further nutrient and water holding capacity.

Soil pH

Soil pH is a measure of acidity or alkalinity. Neutral soils have a pH close to 7, which is ideal for most garden plants. As soils become more acidic, the major elements of nitrogen, potassium and phosphorous become less available.

Some nitrogen-based fertilisers can increase soil acidity, while continual use of lime or laundry greywater will increase alkalinity.

Some plants are adapted to particular soil pH levels. Check the soil’s pH before you apply fertiliser to any plant that is in poor condition. Test kits are widely available (from nurseries or garden centres) and inexpensive.