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Soil Sampling

The major benefit of grid sampling is that a field map can be prepared for each nutrient which can facilitate variable rate fertilizer application. However, the cost of analyzing the required number of samples makes this technique uneconomical for many producers.

Figure 3.3.8 Grid Sampling Pattern

Selecting the Appropriate Soil Sampling Strategy

The suitability of various sampling strategies is based on field variability or sampling intensity, relative cost and the amount of information desired (Figure 3.3.9).

Source: Kryzanowski, 2007

Figure 3.3.9 Suitability of the Various Sampling Strategies

Soil Sampling and AOPA

Under AOPA, confined feeding operations (CFOs) in Alberta that apply less than 500 tonnes (550 tons) of manure, compost or composting materials annually are exempt from the required soil analysis prior to land application. However, producers applying more than this amount require a soil analysis for fields scheduled to receive the material. For these fields, a test no older than three years is required (with the exception of soil texture, which is a one-time analysis) and must include: Extractable nitrate nitrogen (NO •

3

-N) in the 0 to 60 cm (0 to 24 in) depth.

Electrical conductivity (EC) in the 0 to 15 cm •

(0 to 6 in) depth.

Handling and Shipping Soil Samples for Analysis

Proper handling of soil samples prior to analysis will help ensure reliable test results. This section will describe proper handling techniques for moist samples, drying samples before shipping, and shipping samples.

Handling Moist Samples

If possible, moist samples should be delivered to the laboratory on the day they are collected. If this is not possible, samples can be refrigerated for a couple of days or frozen for a longer period. Refrigerating or freezing the samples stops microbial activity. This activity could result in nutrient transformations and affect the results of the analysis. Ensure moist samples spend no more than two days in transit.

tip

Prior to soil sampling, contact the soil testing laboratory for more information regarding handling and shipping soil samples. In many cases, the lab will provide collection containers and/or shipping bags along with forms requesting information on cropping and management history of the sampled field. This information is used with test results to develop fertilizer recommendations. Some labs offer reduced rates for large numbers of samples or may pay the shipping costs.

more info

For more information on soil analysis requirements and other requirements under AOPA, search Ropin’ the Web (keyword: AOPA), or contact the Publications Office

in Edmonton (1-800-292-5697). Field variability

High Low

Directed random

Benchmark

Random composite

Directed benchmark

Grid

High Low

Sampling intensity