PO 20. Describe soil sampling strategies.

Random sampling is appropriate for fairly uniform fields 10 acres or less in size.  2-3 samples per acre should be taken in a random pattern that covers the field, which reduces the risk of sampling multiple soil types within a field.

Grid-based sampling is useful when there is large within-field variability, if that variability is within the responsive range for nutrients and pH, and if the farmer has the ability to manage based on this variability.  The field is divided into small blocks (grid cells of about 1-4 acres each) and a separate sample (consisting of 6-10 sub-samples) is taken from each of these grid cells.  Sub-samples may be taken from a small area at the center of the grid cell, or taken randomly from throughout the grid cell.  Sample results are compiled either directly into a map showing the different soil test levels and recommendations for each grid cell, or the test results may be statistically smoothed to create a map.

Soil type-based sampling is similar to grid-based sampling, in that a field is divided based on soil type, and samples are taken randomly from within those different areas.