wrote this up in a different forum, but it is loosely related to the original question. I think soils are the next frontier for arborists
"Soils with high sand content are generally less susceptible to compaction because of the abundance of macropores. However, you find greater soil fertility (or the ability of the soil to hold nutrients available for plant uptake) in soils with at least some clay percentage and organic matter content (in this case you have 1 to 2 percent OM which is actually pretty good). Good soil aggregation (often a result of undisturbed, non-compacted, non-tilled etc.) is important because these micropores are intact and the increased surface area provides greater surface for the process of cation exchange (nutrient uptake) and hold water in the soil better than the larger macropore spaces between sands and silts where it is more easily leached out. When you crush the soil you effectively reduce the amount of micropore space which translates to destroying soil aggregation. Soil aggregates can be thought of as large ‘clumps’ of clay and silt and sand that hold thousands of small macro and micropores in these ‘clumps’.
Although this soil type at Fiddler’s place is high in sand content, and less prone to compaction as a result, the percentage of clay still merits using a soil amendment to help form and maintain soil aggregation. Gypsum or calcium sulfate, is a great amendment as it helps flocculate the soil. Cations and anions (positive and negatively charged ions) are added to the soil and the charged surfaces of the clay are held together like a bridge by these ions in the soil. These bridges are typically weak van der waal forces but still hold the particles together to form micropores to increase nutrient availability, water retention, and general soil health.
Mulching is also a good ideas as it adds to soil organic matter and helps create a suitable environment for soil biota that help breakup and ‘till’ the soil without crushing or destroying aggregation.
Hope that helps!
In response to the topsoil comment, I would add mulch to increase the organic matter content and hence decrease bulk density and increase pore space, etc etc etc. Add gypsum to the picture and you've just saved a lot of wasted effort by trying to put holes in the soil yourself and probably destroying aggregation (this has to do with why scientists are suggesting farmers till less to improve soil quality) in the process."
jp
