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Physical Properties: Rock
Rock is defined as mineral material greater than 2 mm in dimension.
Particles smaller than 2mm are defined as soil particles. Restoration
sites commonly have earthen materials elevated in rock content that
impart a strong influence on the quality of growth media. Often
"minesoils" or "coversoils" are distinguished from "topsoil" by
their abundance of rock, lack of structure and lack of biological
activity. Since rock is essentially non-participatory in the biological
function of soil, any added rock only takes away from the potential
productivity growth media. Rock does not contribute nutrients to
the soil in anything other than the smallest amounts, rock does
not hold water which may become available to plants (with some exceptions)
and rock is tough on tillage equipment.
Rock can be removed from soil material with commercial implements,
but this practice in infrequently employed. Typically, rock is part
of the final rootzone. Compensating for this loss in soil quality,
additional soil amendment can be added. Conversely, expectations
for vegetative growth can be lowered. Rocky soils without amendment
typically result in sparse vegetation cover. Rocky soil substrates
also mandate the use of robust construction equipment. Farm implements
designed for agricultural soil have a greatly reduced lifespan when
used in rocky minesoils. Accelerated maintenance and construction
hold-ups can be expected when tilling and seeding into rocky soil.
How much rock is too much? It depends on many factors, especially
moisture. When adequate moisture is available for plant growth,
higher levels of rock can be tolerated. When a site is droughty
and rocky, the prospect exists for minimal plant growth. In dryland
sites of the western U.S., 50% rock content is excessive, 40% is
marginal, 30% is difficult and 20% and less is preferred.
Problem | Compliance
| Health & Safety | Sampling
| Analytical | Data
Quality
Site Assessment | Prediction
| Construction | GIS
| Monitoring & Assessment
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