Agriculture Reference
In-Depth Information
Fimic epipedon
A+AB
(
≥
25 cm)
P-accumulated agric horizon
Anthropogenic horizon
B
p
(
≥
10 cm)
B
Cambic or other horizon
Natural horizon
C/R
Parent material or bedrock
Figure 10.12
Sketch of the profile of Typic Fimic Anthrosols. (From Gong et al., 1999. With permission.)
Fimic Epipedon
The Ýmic epipedon is an anthropic surface horizon with high mellowness formed by long-term
plantation of vegetables, application of large amounts of night soil, manure, organic trash, etc., and
intensive cultivation and frequent irrigation (Figure 10.12).
A Ýmic epipedon meets the following requirements:
¤a thickness of 25 cm or more, in which the upper part is highly Ýmic subhorizon and the lower
part is transitional Ýmic subhorizon
¤ the weighted average of organic carbon being 6 g kg
-1
or more
¤ the weighted average of extractable P contents (by 0.5 mol L
-1
NaHCO
3
) being 35 mg kg
-1
or more
(80 mg kg
-1
or more P
2
O
5
)
¤having large amounts of worm casts, and wormholes with intervals of less than 10 cm, which
occupy half or more of the total
¤having coal cinders, charcoals, brick or tile fragments, ceramic pieces, and other artiÝcial intrusions
Agric Horizon
An illuviation horizon formed by cultivation in upland soils, the agric horizon directly underlies
the plough horizon, and is generally derived from one or another diagnostic subsurface horizon. It
meets the following requirements:
¤a thickness of 10 cm or more
¤
one of the following:
¤ macromorphologically, having humus-clay or humus-silt-clay coatings on voids and ped faces
with both of color value and chroma lower than those of matrix, which are darker and as thick
as 0.5 mm or more, and account for 5% or more by volume; or micromorphologically, with
coatings which account for 1% or more in thin section, or higher color value and lower chroma
in chromic soils than those of underlying layers, and the hue does not change or becomes a
little yellower
¤a higher or much higher pH and base saturation in the acid soil in this horizon than in underlying
horizon, which is not inÞuenced by illuviation due to cultivation
¤a phosphorus content (extracted by 0.5 mol L
-1
NaHCO
3
) of 18 mg kg
-1
or more in Ýmic soils,
which is much higher than that in the underlying horizon
