Title : Oxisol
Size : 12 X 24 inches
Date : 2009
Medium : Acrylic
Support : Canvas
Signed: Yes on the front and back
Framed: YES!
It will be framed in a black floater frame. I should have it back framed by the begining of next week.
Oxisol
From Wikipedia, the free encyclopedia
Oxisols are an order in USDA soil taxonomy, best known for their occurrence in
tropical rain forest, 15-25 degrees north and south of the
Equator. Some oxisols have been previously classified as
laterite soils.
The main processes of soil formation of oxisols are
weathering, humification and
pedoturbation due to animals. These processes produce the characteristic
soil profile. They are defined as soils containing at all depths no more than 10 percent weatherable
minerals, and low
cation exchange capacity. Oxisols are always a red or yellowish color, due to the high concentration of
iron(III) and
aluminium oxides and
hydroxides. In addition they also contain
quartz and
kaolin, plus small amounts of other
clay minerals and
organic matter.
The word "oxisol" comes from "oxide" in reference to the dominance of oxide minerals such as
bauxite. In the
FAO soil classification, oxisols are known as ferralsols.
Scientists originally thought that the heavy vegetation of tropical
rain forests would provide rich nutrients, but as rainfall passes through the litter on the forest floor the rain is
acidified and leaches
minerals from the above soil layers. This forces plants to get their nutrition from decaying litter as oxisols are quite infertile due to the lack of organic matter and the almost complete absence of soluble minerals
leached by the wet and humid
climate.
Present-day oxisols are found almost exclusively in tropical areas of
South America and
Africa, almost always on highly stable continental
cratons. In
Australia vast areas formerly covered in rainforest have become so dry that oxisols have formed a hard
ironstone cover upon which only
skeletal soils can form.
Fossil oxisols are known from the first appearance of free
oxygen in the
atmosphere about 2200 million years ago. In warm periods like the
Mesozoic and
Paleocene, oxisols extended to areas that now have quite cool climates, extending well into
North America and
Europe. It is believed oxisols became vegetated later than
ultisols or
alfisols, probably because vegetation took a long time to adapt to the infertility of oxisols.
Oxisols are often used for tropical crops such as
cocoa and
rubber. In some cases,
rice is grown on them. Permanent cropping of oxisols in low-income areas is very difficult because of low
cation exchange capacities and high
phosphorus fixation on iron and aluminium oxides (ligand exchange mechanism;
inner sphere complex with phosphate). However, many oxisols can be cultivated over a wide range of moisture conditions. On this account, oxisols are intensively exploited for agriculture in some regions which have enough wealth to support modern agricultural practices (including regular additions of
lime and
fertilizer). A recent example of exploitation by modern methods involves the growing of
soybeans in
Brazil.
Oxisols are divided into the following suborders:
Aquox - oxisols with a water table at or near the surface for much of the year
Perox - oxisols of continuously humid climates, where precipitation exceeds evapotranspiration in all months
Torrox - oxisols of arid climates. Because the present climate can never produce enough weathering to produce oxisols, torrox soils are always
paleosols formed during periods of much wetter climates. They occur mainly in
Southern Africa.
Ustox - oxisols of semiarid and subhumid climates
Udox - oxisols of humid climates
