Use two buckets and an auger or spade.
To get a representative sample of the topsoil and subsoil layers, use separate buckets for topsoil and subsoil. The topsoil sample is usually taken from the top 30 cm of the soil. The subsoil sample is taken from the profile between 30 cm to 60 cm – 100 cm down, depending on the structure of the roots of the crop that is being planted and how deep you plan to plough. If the root structure is shallow, taking samples from the topsoil may be necessary. However, to also unearth the deeper profile will give a better indication of the drainage capacity of the soil.
Three representative samples per hectare will be needed. First, look at the area you want to work in to see if there are any apparent differences in soil structure. If there are, samples should be taken from all soil structures. If the soil looks homogeneous (the same), take samples from all over the area. First, clear the surface of any debris, such as grass and other organic material. Also, avoid footpaths or places where animals have defecated or urinated, as this can affect the sample. Work in a Z, S or W pattern over the sample area. It should only cover the area and any different ground structures visible.
Choose a representative sample from the bag that weighs around 1 kilogramme by taking ten sub-samples from your chosen location, combining them in a clean plastic bag, shaking and mixing the bag thoroughly (so there will be three representative samples per ha).
Remember not to bring your hands into contact with soil as any debrise can affect the sample’s results; pull a plastic bag over your hands when working with a soil sample.
Use of an Auger:
Use of a spade:
If you use a shovel to collect samples, first make a square hole with clean, smooth sides so that one can see the profile to the desired depth. Take the spade and scrape upwards from the 30 cm mark to have a two to three-cm layer from the side of the hole in the spade. Pour it into the topsoil bucket. Repeat the same procedure from the tree of the hole to the 30 cm mark, making sure not to drop any topsoil into the shovel. Place this soil in the underground bucket.
Repeat this process for all the identified sample locations and pour all the topsoil into one bucket and all the subsoil into the other bucket. Once samples have been collected, each in its bucket, mix the soil in each bucket well.
Namib Laboratories will do the analysis and should provide you with the required sample size, usually 1 kg. Now take the required amount of sand from each bucket, and place it in the appropriately marked plastic sample bags to be delivered to the laboratory as soon as possible.
Figure to illustrate a pattern of sampling:
