Figure 3-11. Extremely Bouldery Soil Surface
An area of extremely bouldery soil (class 3).
Fragments on the Surface
This section discusses the description of rock fragments (especially stones and boulders) that are on the soil as opposed to in the soil. The description of gravel, cobbles, and channers (≥ 2mm but < 250 mm in diameter) differs from that for stones and boulders (≥ 250 mm in diameter) because an important aspect of gravel, cobbles, and channers is their areal percent cover on the ground surface. This cover provides some protection from wind and water erosion. It may also interfere with seed placement and emergence after germination. For stones and boulders, the percent of cover is not of itself as important as the interference with mechanical manipulation of the soil. For example, a very small areal percentage of large fragments, insignificant for erosion protection, may interfere with tillage, tree harvesting, and other operations involving machinery.
Class 3.—Stones or boulders cover 3 to less than 15 percent of the surface. The smallest stones are as little as 0.5 meter apart; the
smallest boulders are as little as 1 meter apart.
Soil Survey Manual, Ag. Handbook 18, 2017, (p. 144).
Figure 3-11. Extremely Bouldery Soil Surface
An area of extremely bouldery soil (class 3).
Fragments on the Surface
This section discusses the description of rock fragments (especially stones and boulders) that are on the soil as opposed to in the soil. The description of gravel, cobbles, and channers (≥ 2mm but < 250 mm in diameter) differs from that for stones and boulders (≥ 250 mm in diameter) because an important aspect of gravel, cobbles, and channers is their areal percent cover on the ground surface. This cover provides some protection from wind and water erosion. It may also interfere with seed placement and emergence after germination. For stones and boulders, the percent of cover is not of itself as important as the interference with mechanical manipulation of the soil. For example, a very small areal percentage of large fragments, insignificant for erosion protection, may interfere with tillage, tree harvesting, and other operations involving machinery.
Class 3.—Stones or boulders cover 3 to less than 15 percent of the surface. The smallest stones are as little as 0.5 meter apart; the
smallest boulders are as little as 1 meter apart.
Soil Survey Manual, Ag. Handbook 18, 2017, (p. 144).