Tool 6.3 - Assessing soil health

Module Index

Module 1 - planning

Module 2 - wool

Module 3 - meat

Module 4 - people

Module 5 - NRM

Module 6 - soil

Module 7 - pasture

Module 8 - grazing

Module 9 - genetics

Module 10 - more lambs

Module 11 - sheep health

Module 12 - pastoral production

Hot Topics

Earthworm sampling tool

1. Using a spade, dig a square of soil to a depth of 10cm. For earthworms it is best to sample in late winter or early spring when it is not too cold or hot and after about 20–25 mm of rain.

2. Sample different areas of the paddock (creek flats, stony ridges etc), taking 8‑10 samples in a typical paddock. If the paddock is very variable more samples will need to be taken.

3. Dig up the soil and break the clods and roots by hand. Count the number of earthworms. In high rainfall permanent pastures, more than 10 in a square (spade width about 20cm) indicates high numbers. If the paddock has been recently cropped or cultivated, numbers will be less. Expect lower numbers in drier areas and years.

4. Record the earthworm numbers and sampling location. Sample again in approximately the same place the following year at the same time of the year to monitor any changes. After sampling, replace the earthworms and soil.

5. If you want to identify the types of earthworms that you have, a useful pictorial guide (Worm Wise II) can be found on the Victorian DPI website at http://vro.agriculture.vic.gov.au/dpi/vro/vrosite.nsf/pages/soil_health_worm_wise

‘Look, smell, feel’ tool

This can be done in conjunction with the earthworm tool or as a separate exercise. Use a spade and dig a square (about 20cm by 20cm) to a depth of 10cm and take 8–10 samples from different areas in the paddock. Record your observations in the table:

The more “Yes” boxes you ticked in the table in the tool, the healthier the soil in the sampled paddocks.

While you can’t change your soil type, you can influence soil quality by increasing groundcover and organic matter levels (see procedure 6.2).

Use this simple table to record your observations for each of the samples taken in a paddock. Repeat the sampling at the same time next year in similar locations in a paddock. Track the trends over time to see if your management practices are also improving the health of your soil.

Other tests

For sandy soils, earthworm numbers may not be an ideal measure of soil biological health. A range of other methods are available, particularly cotton strip assays, which can provide a measure of how rapid stubble like material may break down in soil. Many labs offer tests to measure soil bacterial and fungal numbers and their activity. However, there is little evidence that the numbers mean anything from site to site or year to year and interpretation of these numbers and ratios is completely subjective.