Sampling Recreational Turf for Soil Analysis

Note Number: AG0395
Published: May 1999
Updated: May 2009

The usefulness of soil analysis depends on representative samples being supplied to the laboratories. Even in small areas which are apparently uniform, soil properties can vary. The standard sampling procedures outlined below are designed to minimise the effects of soil variation and help you collect a representative sample.

Sampling methods

Soils are generally sampled by driving a sampling tube into the soil, usually to 100 mm depth, and extracting a soil core. To obtain a representative sample, soil cores are combined from a large number of places within the sample area. The more cores that are combined, the more representative the final sample will be and the better the advice that can be given. At the completion of sampling, fill the holes that have been created with an appropriate soil mixture.

Depth of Sampling

When sampling soils it is important that the standard sampling depths are used. In the case of surface soil samples this depth is usually 100 mm. Shallower sampling will often result in higher values for chemical tests because the amount of nutrients is usually greater near the soil surface.

Sampling areas prior to planting new turf

When sampling soil proposed for use in establishing new turf it is recommended to sample at a time when the seedbed is as close to final preparation for sowing as practical; allowing time for soil analysis and reporting and the ordering and delivery of fertiliser.

Selecting areas for sampling

Soil sampling from under established turf is often performed when a specific problem requires investigation. In such circumstances it is best to consult An appropriately trained professional to determine whether additional tests such as Plant Tissue Analyses are required for a correct diagnosis. When sampling a specific problem area, it is often helpful to contrast the situation by taking a sample from a non-problem area as well, for example good and poor sections of turf.

General sampling guidelines for recreational turf

• Using a sampling tool take 30 cores at sites evenly distributed over the area to be sampled. A grid pattern should be used to determine  site locations (see Figure 1).
• Remember you are trying to get an "average" sample that is representative of the entire area. Avoid heavy wear areas such as centre circles on recreation ovals, areas of unusual growth or where grass clippings, fertiliser, lime or gypsum have been dumped. Poorer spots should only be sampled if they are numerous. It is best not to sample close to boundaries or other obstacles which are not representative of the area, particularly where lime has been used for ground marking. Fertiliser takes a little while to be incorporated into  soil so it is also best not to sample soils which have had fertiliser, gypsum or lime applied within six weeks. Never sample areas which have had fertiliser, gypsum or lime applied in the past two weeks. Where soils have been prepared for planting, firm the soil with your foot prior to sampling to ensure you get a sample from the appropriate depth.
• Take cores from 0-100 mm (0-4 in) depth on recreational ovals and 0-75 mm (0-3 in) on bowling greens. Remove each core carefully from the sampler using a clean screw driver or similar tool and place it in a clean plastic sample bag. If only part of the core comes out of the sampler discard that core and re-sample that site.
• At least 30 cores should be taken from the area being sampled. The more cores that are taken the more representative the sample will be.
• If you have more than the amount of sample required by the laboratory it will be necessary to sub-sample. Place the sample in a clean container, break up the clods and spread the total sample evenly on a clean bench. Divide the sample into four quarters, discard the two diagonal quarters and place the remaining sample in a clean container.
• Transfer the cores or the sub-sample to a clean sample bag if you have not already done so and seal the bag. Mark the bag with an identifying name, the number of cores taken and the depth of the sample.
•  Your samples are now ready for dispatch to the laboratory. Be sure to provide all the information requested by the laboratory processing your samples to ensure that the best possible recommendations can be made.

Figure 1. Recommended sampling pattern for receational turf.

Sub-surface Soil Sampling

Sampling of the sub-surface soil may be required where:

• a soil structural problem is suspected;
• salt is suspected of being a problem; or
• soil drainage is impaired.

It is recommended that sub-surface samples are taken from 100-300 mm (4 - 12 in) if the soil is uniform in colour and texture with depth. Where soils vary with depth, for example where different foundation materials have been used, the different layers should be sampled separately.

When collecting samples be careful not to contaminate the subsoil samples with scrapings from other soil layers. Because the chemical properties of soils vary dramatically with depth, even minor contamination of subsoil samples can make the interpretation of chemical results very difficult.

Sampling soils to be used for topdressing or construction

Take 30 representative samples from the middle, top, bottom, inside and outside of the heap. Combine the samples into one and sub-sample if necessary (see step 5 of the General guidelines).

Additional information

More information on soil analyses and sampling is available from your local district office of DPI.

Acknowledgements

This Agnote was developed by David Nash and Austin Brown, May 1998.
It was reviewed by David Nash,  May 2009.