How to use your soil corer

Diagram for the correct use of a soil corer.

The last issue of Ground Cover told you how to make a corer for testing the moisture and structure of your soil. This issue tells you how to use it. In our next issue we'll tell you how to assess how much water is in your soil and what that tells you about rainfall and other indicators

Using the corer

Before driving the corer into the topsoil, brush away loose dry soil from the site, to prevent it falling into the corer and jamming the soil inside the tube. Start with a one-metre-long corer, and drive it in with a 8-10 kilogram wooden donger.

Use a jack and chain to pull out the corer, then use a longer corer of smaller diameter if you want a deeper sample. If the upper soil layer is wet enough or loose enough to threaten jamming it may be easier to take only a 30 cm core at first and repeat from there.

Removing the core

You will need a semi circular cutting tray made by cutting a length of 75-100 mm PVC pipe lengthwise (see below). Hold your hand over the top end of the corer and tilt it so that the core slides down to that end. You may need to push the bottom of the core inwards to free it from the cutting edge, then remove the core from the tube either by allowing it to slide out into the cutting tray or pushing it out with a wooden rod if necessary (see diagram).

With the core laid out in the cutting tray you can identify such features as the depth and feel of different layers and the location of roots. You can also measure pH values at various depths.

The first thing to look for is the accumulation of organic matter at the surface, shown by a dark brown or black colour.

If there is 'plant available water' a clay core will be soft and workable, but where there is no available water it will be hard and impossible to shape. With practice, you can estimate available water by the length of the core which is soft, but it is also possible to measure this accurately.