A critical step in obtaining accurate soil tests is collecting representative samples in situ. Typically, uniform plots should be sampled in a simple random pattern across the field collecting at least 15-20 equal size soil cores to various depth. Alternatively, sampling transects can be installed. Avoid, or sample separately, areas which are obviously different like roads, eroded spots, low areas, and wet spots. In general, plots with significant landscape or other differences should be divided into separate sample areas. Differences may include soil types, slope, degree of erosion, drainage, land use history, or other factors that may influence results. More intensive sampling should be used where detailed information about within plot variability is needed.

Laboratory tests are calibrated to specific depths. It is vital to collect samples from appropriate depths because a core taken deeper or shallower will generate erroneous results. Sampling depth for most agricultural soils is typically the tillage depth, more skeleton-rich (forest) soils are often sampled to at least 30 depth, 10 of those mineral soil if large organic layers occur. The surface soil samples are typically used for conventional tests of organic matter, phosphorus, potassium, pH, and salt levels. Studying deep-rooted species such as wheat and barley might need deeper samples, e.g. to study nitrogen availability. Be sure to separate surface litter. Subsoil samples are often needed to estimate available nitrogen and to determine C stocks. Both surface and subsurface soil samples are needed to estimate root system depth distribution.

A stainless steel soil sampling probe / soil corer is the most commonly used tool for collecting soil samples under normal conditions. The soil probe provides a continuous soil core with minimal disturbance to the soil that can be readily divided into various sampling depths.Specific storage solutions are available to transport intact soil cores to the laboratory. Even if compression in larger diameter soil corers can be small, any soil compression has to be avoided for determining soil density, thus specific soil ring samplers are used in a horizontal fashion in soil pit walls for soil density. Vehicle-mounted hydraulic probes are available and are a better choice under adverse soil sampling conditions if acees to the sampling site is provided and slope permits. Other tools include plastic sample bags, a tape measure / ruler to determine potential compression and  a water proof marker for labelling. See the VSI soil corer manual for a comprehensive tools / packing lists for a soil sample campaign.

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