A soil sample must represent a uniform area. Differences in texture (sand, silt, clay), color, slope, degree of erosion, drainage, past management practices (fertilization, crop rotation, etc.) should be taken into account when collecting the sample. At the same time, waterways, terraces, fence rows and unusual spots should not be included in the samples collected for a neighboring field or garden site. Those areas, however, could be tested separately if a crop is to be planted in those areas.
Samples can be collected with a soil probe, soil auger, shovel or trowel. The key is to use a clean, rust-free tool to avoid the contamination of the sample with iron. Collect the sample from the soil surface to the depth desired, typically to the plow depth (usually 8 to 12 inches). A clean plastic pail is a good container to place and mix the soil samples in. Avoid using galvanized or brass containers or the sample will be contaminated with zinc. The resultant soil analysis could indicate a sufficiency of these contaminates when a deficiency actually exists.