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I have heard this from property owners for years "Why is the dirt in my yard so Hard?" or "why is it so lousy?" The answer to this question is found in the way buildings, structures, roads, and construction projects occur.
When construction occurs there are standards met to insure that homes don't sink and other structures fail related to a standard called ASTM D1557.
The requirements for compaction are typically specified with reference to the ASTM D1557 "Modified Proctor" moisture density curves for the soil in question. Effectively, the test produces a curve identifying the optimum moisture-density and a plot indicating predicted densities at various moisture contents.
90% compaction is the commonly specified backfill requirement for nonstructural areas.
95% is often specified for roadway embankments and fills under other structural areas sensitive to settlement.
98% is often specified for fills under critical structural elements.
Lower moisture contents aid compaction by reducing friction between particles. This effect increases up to the “optimum moisture” content. At higher levels the incompressible fluid occupying the voids actually limits consolidation.
Soil types with finer particles sizes e.g. clays or silts drain poorly and retain water once saturated. Better draining sands may actually consolidate with water flowing though the soil and moving particles into voids; this is a common cause of settlements.
So consider this, plants need about 21% oxygen content in the soil to grow and thrive, but your home if built after 1963 was compacted to at least 90%, which only 10% Oxygen content.
There are ways that we can increase the oxygen content in the soil. One is hollow tine core aeration to the lawn at least 1 time a year and hopefully twice a year. Keep in mind with hollow tine core aeration you need to average 8-12 holes per square foot.
If you are landscaping or adding plants make sure you or your landscape contractor does proper soil and bed preparation with deep tillage with 2" of organic matter added . Using organic composted mulches is critical at improving the soil long term. Make sure that all landscape plantings conform to the ANSI A300 part 6 standard of planting which demands that hole size at the time of planting is at least 1.5 times wider than the root ball.
I would further suggest you work with a 3rd party verifier like a "Certified Arborist" that projects and work done conforms to what is suggested above, other wise you are just planting plants to die in soils with not enough Oxygen to support a plants roots system.
If you have existing plantings your landscape should under go a "Soil Compaction Test" to determine how bad it is and how to correct it. Soil compactions levels are a directly related to lack of available Oxygen in the soil and the compaction that occurred years prior.
To find a Certified Arborist go to www.treesaregood.org