Agriculture Reference
In-Depth Information
Aridosols.
Aridosols are soils that have an aridic epipedon and one or more diagnostic subsurface
horizons, such as salic horizon, salipan, gypsic horizon, calcic horizon, argic horizon, or cambic
horizon, within 100 cm of the mineral soil surface. The aridic epipedon is a surface horizon with
special morphological differentiation formed under an aridic moisture regime, and has one of the
following land surface features:
¤
desert pavements consisting of gravel or stones with varnish or wind carving striae
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sand layerÏsand gravel layer or small dune
¤
polygonal cracks and organic crusts with dark color
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bare land with polygonal cracks Ýlled with sands and/or silts grains; very thin clay capping on the
top surface of polygons; does not have a salic or natric puffed crust or the mixed layer of soils
and salts from the surface; has a puffed crust with a thickness of 0.5 cm or more from the surface,
or a sheet layer in squama structure
Aridosols occur mainly in arid regions of northwest China and in the Qinghai-Xizang Plateau.
They cover a large area of 2,020,000 km
2
.
Halosols.
Halosols are soils that have a salic horizon within 30 cm of the mineral soil surface
or an alkalic horizon within 75 cm of the mineral soil surface. The salic horizon is at least 15 cm
thick, has a salt content of 20 g/kg or more in arid regions or 10 g/kg or more in other regions,
and has a product of salt content multiplied by the thickness, equaling 600 or more. Halosols occur
mainly in arid, semiarid, and desert regions of northern China. Their area totals about 312,000 km
2
.
Gleyosols.
Gleyosols are soils that have a horizon (>10 cm thick) with gleyic features (violently
reduced features due to long-term water-logging) within 50 cm of the mineral soil surface. These
soils are distributed in depressions, low land, Þood land, and valleys. Their total area in China is
94,400 km
2
.
Isohumosols.
Isohumosols are soils that have a mollic epipedon and isohumic property and
base saturation of 50% or more. They occur mostly in grassland and meadowland in semiarid and
temperate regions. They cover an area of 624,000 km
2
.
Ferrosols.
Ferrosols are soils that have a LAC-ferric horizon within 125 cm of the mineral soil
surface. This LAC-ferric horizon is a horizon formed in the preceding moderate ferralization, and
which contains low-activity clay and free iron oxides, and is at least 30 cm thick. It has a texture
of sand loam or Ýner, and has a clay content of 80 g/kg or more. It has a hue of 5YR or redder,
or a DCB extractable iron content of 14 g/kg or more in Ýne-earth clay, and has CEC of < 24 cmol
(+)/kg clay in subhorizons (10 cm or thicker). It does not meet the requirements of a ferralic horizon.
These soils occur mainly in southern China, in central and southern subtropical and tropical regions.
Their area totals about 350,000 km
2
.
Argosols.
Argosols are soils that have an argic horizon or claypan with illuviation cutans within
125 cm of the mineral soil surface. Argosols are distributed in the central and northern parts of
eastern China, in areas inÞuenced by monsoonal climate, mainly in low mountains and hills. Their
area totals 558.000 km
2
.
Cambosols.
Cambosols are soils that have a cambic horizon, which has no illuviation of
materials and no argilliÝcation, and has a color of brown or reddish-brown or red, yellow or purple,
etc., and has a weakly developed B horizon, or has one diagnostic subsurface horizon (e.g., albic
horizon, calcic horizon, etc.) within 100 cm of the mineral soil surface. These soils occur throughout
the country, mainly in the east and south of the Qinghai-Xizang Plateau and in the Huang-Hui-Hai
Plain. They cover the largest area of the 14 dominant soil orders, 2,320,000 km
2
.
Primosols.
Primosols are soils that have one surface layer and no diagnostic subsurface horizon.
Primosols occur extensively in China, with an area totaling 608,000 km
2
, commonly in the semiarid
and arid regions of northern China and the Sichuan Basin. The Sketch Soil Map of China (compiled
by CSTC Group, ISSAS) shows the broad distribution of the soil orders as mentioned above.
