Page 95 - Nutrient Management Planning Guide

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Soil Sampling

tip

Before sampling or having a field sampled, be sure to identify the location of any underground utilities. Failing to identify these can result in personal risk and financial liability.

Call Alberta One-Call at 1-800-940-3447 before sampling to have underground utilities identified.

tip

Core samplers allow reliable separation of sampling depths. Auger type samplers result in too much mixing between sample depths, resulting in poor soil samples.

Photos courtesy Crystal Korth, AF and Natural Resource Conservation Service

Figure 3.3.2 Manual and Truck Mounted Soil Sampling Probes

To collect a quality sample, insert the sampling probe straight into the ground (Figure 3.3.3). Avoid inserting the probe on a slant, because this will reduce the accuracy of the sample.

Figure 3.3.3 Correct and Incorrect Insertion of a Soil Sampling Probe

Sampling Depth

It is recommended that samples be taken from the following depths to get the best estimate of soil nutrient levels to optimize nutrient management:

0 to 15 cm (0 to 6 in) • 15 to 30 cm (6 to 12 in) • 30 to 60 cm (12 to 24 in) •

Soil testing laboratories can develop fertilizer recommendations from a 0 to 15 cm depth sample, but these recommendations make assumptions about nutrient content in deeper layers. More reliable fertility recommendations and better nutrient management decisions can be made when nutrient levels are measured rather than estimated (e.g., for nitrogen and sulphur).

Sampling for Nitrate and Sulphate

Nitrate nitrogen (NO

3

-N) and sulphate sulphur (SO

4

-S) are mobile nutrients that may be found in significant amounts in the 15 to 60 cm depth. Therefore, N and S fertility recommendations should be based on extractable NO

3

- and SO

4

-2 contents in a 0 to 60 cm deep soil sample. Nitrogen and S recommendations could be incorrectly estimated if they are solely based on a 0 to 15 cm depth sample. Separate sample depths provide more reliable estimates of NO

3

-N and SO

4

-S in the soil profile.

Sampling Tools

Soil sampling tools (Figure 3.3.2) can be purchased from equipment supply companies. Alternatively, sampling equipment can be borrowed from fertilizer dealers, private labs, or crop advisors. For samples deeper than 30 cm (1 ft) truck mounted hydraulic coring equipment is recommended. Many fertilizer dealers offer soil sampling services.