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Collect soil samples for testing
More site evaluation and soil tests will be needed in a landscape that has been highly urbanized or disturbed than in an undisturbed site. Without a soil management plan, poor-quality subsoil often ends up as topsoil on these disturbed sites.
Rubble and other debris can become mixed with soil making the mix ill-suited for tree growth. Separate soil tests should be conducted wherever you have reason to believe the soil is different.
You may collect soil data about the site using soil surveys available at the Soil Conservation Office. Soil surveys describe the peculation rate, hardpan characteristics, slope, soil type and in some cases the trees that naturally grow on the soil type. These are most useful for residential developments carved out of woodlands or agricultural fields or other relatively undisturbed sites.
A more focused, on-site soil evaluation is needed for most urban and suburban landscapes where soil has been moved with heavy equipment. For example, soil in each sidewalk cutout along a street may need to be evaluated separately because conditions often vary greatly.
You may test soil in three cutouts and find it well drained. The other 15 or 20 cutouts at the site that you did not test may have poor drainage. If you were to base your tree selection decisions on the three cutouts you tested, you might choose a tree requiring good drainage for survival. The planting is likely to fail because most trees would drown.
Holes for testing soil attributes can be dug with a backhoe and/or soil auger. A backhoe is preferred because you can see a large portion of the soil when the hole is dug.
Specific guidelines on the proper number of soil tests are impractical because each site is unique. Uniqueness requires judgment on your part. For example, many residential sites in clay soil become compacted during construction, whereas those in sandy soil may not. Therefore, a more detailed evaluation of soil attributes is often required in clay soil.
Professional judgment of a
local soil specialist, horticulturist or urban forester can provide unique clues
into the nature of the soil, and can begin to list the trees likely to grow
well at the site.
