How to Collect Garden Soil Samples

A soil test is only ever as good as the sample submitted, so it is critical that you use the right method to collect garden soil samples.

To be effective, a soil test needs only one thing above all else – consistency! In the beginning, choose the area(s) of the garden to sample and keep going back to them with every round of testing. You should also follow the same path across your chosen area and use the same sample depth each time.

The objective is to look for a ‘Representative average’ for a particular area. The areas of a garden to focus on will depend on what is growing there. You can use the plan below as a guide. A vegetable or kitchen garden (dark green area below) would be one area, the flower beds (tan areas below) another. For a general purpose test (especially for a new garden) focus on the lawn areas (light green below). When specifically sampling around trees (as opposed to the lawn area they are growing in), collect the cores from the "Drip-line" region, that is, the area beneath the outmost branches. Most importantly you need to use the right implement and sample to the right depth.

Above: a garden layout showing the general areas that can be sampled for testing, each with a different colour.

Collecting the Sample

Remember, you are looking for results that give a reasonable picture of the soil within the root zone of the plants. For gardens the proper depth to sample is from the surface down to 15cm.

In all cases, the best tool to use is a stainless steel core sampler - a simple apple corer that you can get from your local Supermarket will suffice. You need to collect soil from 20 – 30 spots across the area of the garden you are interested in, mix the soil VERY thoroughly in a clean plastic bucket and take the sample (about 250g) out of this. This is best packed in a sealed plastic bag.

NB. Only use stainless steel samplers. Other metals can produce distorted results for Iron, Copper or Zinc, etc.

Research shows that a zigzag path gives the most reliable result, but choose your path carefully, so you can easily go the same way again next time.

Lastly, don’t forget to complete the information sheet with important sample and site details.

Wet Samples

It is no good to take the soil sample if the soil is saturated, (that is, if water is dripping out when you hold a handful of soil in your hand).

If the soil is just damp, but not saturated, it can be put on a plate or in a paper bag, and let dry either in the sun or in the oven over night with the absolute maximum temperature between 45° and 60° Celsius.

Sending a Soil Sample to SWEP

We can send you a FREE sample kit, but if you already have your sample, you should enclose a Sample Information form and payment (or Order Online). Please download and print either the Australian Garden Soil Details Form or the International Garden Soil Details Form to send with your samples. We accept either Cheques (within Australia), Credit Card or Online Payment - Do Not send Cash in the Mail! Your local Post Office is probably the best to advise on how to pack and label the sample. Having done this, mail the sample, together with your payment or PayPal receipt and information sheet to SWEP.

For customers within Australia, the address to send samples is :

SWEP Analytical Laboratories
PO Box 583, Noble Park, VIC 3174
Australia.

Please Note: Additional details need to be included on the package if you are sending samples from Outside Australia.