Ashburn consists of moderately deep and moderately well drained soils on broad, convex interfluves in the Culpeper Basin of the northern Piedmont. These soils formed in reworked alluvium and the underlying red Triassic interbedded siltstone, fine-grained sandstone, and shale residuum. The taxonomic class of Ashburn soil is fine-silty, mixed, active, mesic Oxyaquic Hapludalfs. The geologic age of the Ashburn area ranges from the late Triassic period's Norian age through the early Jurassic period's Hettangian age, or about 220 million years ago.
Climate and Vegetation
The mean annual air temperature ranges from 49 to 57 degrees F. Mean annual precipitation ranges from 35 to 45 inches. Ashburn soil and climate are suitable for row crops and hay crops. Some woodland of northern red oak and Virginia pine remain.
Slopes range from 0 to 8 percent. Solum thickness ranges from 18 to 40 inches. Depth to bedrock is 20 to 40 inches. Rock fragments of rounded vein quartz and red siltstone channers range from 0 to 5 percent in the Ap and Bt horizons. Rock fragments of red siltstone channers range from 0 to 35 percent in the 2Bt and 15 to 55 percent in the 2C horizons. Reaction is very strongly acid through moderately acid.
Ap - 0 to 8 inches; yellowish brown (10YR 5/4) silt loam; moderate fine granular structure; friable, slightly sticky, nonplastic; strongly acid; abrupt smooth boundary (2 to 10 inches thick)
Bt1 - 8 to 26 inches; yellowish brown (10YR 5/6) silty clay loam; moderate fine subangular blocky structure; firm, slightly sticky, slightly plastic; many faint clay films on faces of peds; common medium distinct reddish brown (5YR 5/3) iron depletions on faces of peds; common medium distinct brownish yellow (10YR 6/8) soft masses of iron accumulation; strongly acid; gradual smooth boundary
2Bt2 - 26 to 34 inches; yellowish red (5YR 4/6) silty clay loam; weak medium subangular blocky structure; firm, slightly sticky, slightly plastic; common distinct clay films on faces of peds; many faint common medium distinct reddish gray (5YR 5/2) and many medium light reddish brown (5YR 6/3) iron depletions on faces of peds; common medium distinct brownish yellow (10YR 6/8) soft masses of iron accumulation; strongly acid; gradual smooth boundary. (Combined thickness of the Bt horizon is 10 to 35 inches)
2C - 34 to 39 inches; red (2.5YR 4/6) channery silty clay loam; massive; friable, slightly sticky, nonplastic; common medium faint reddish brown (5YR 5/4) soft masses of iron accumulation on surfaces of rock fragments; 30 percent siltstone channers; moderately acid; clear smooth boundary. (0 to 10 inches thick)
2R - 39 inches; hard red siltstone bedrock
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