- Soil morphology
Soil morphology is the field observable attributes of the soil within the various
soil horizons and the description of the kind and arrangement of the horizons. [cite book | last = Buol | first = Stanley W. | authorlink = | coauthors = Southard, Randal J., Graham, Robert C., and McDaniel, Paul A. | title = Soil Genesis and Classification, 5th Edition | publisher = Iowa State Press, A Blackwell Pub. Co. | date = 2003 | location = Ames, Iowa | pages = 494 | url = | doi = | isbn=0-8138-2873-2] C.F. Marbut championed reliance on soil morphology instead of on theories of pedogenesisfor soil classificationbecause theories of soil genesis are both ephemeral and dynamic. [cite book | author = Soil Survey Staff | title = Soil Survey Manual | publisher = U. S. Government Printing Office | date = 1993 | location = Washington D.C. | url = http://soils.usda.gov/technical/manual/ | format = HTML| doi = | id = Soil Conservation Service, United States Department of AgricultureHandbook 18 |accessdate = 2006-11-03]
The observable attributes ordinarily described in the field include the composition, form,
soil structureand organization of the soil, color of the base soil and features such as mottling, distribution of roots and pores, evidence of translocated materials such as carbonates, iron, manganese, carbon and clay, and the consistence of the soil.
The observations are typically performed on a
soil profile. A profile is a vertical cut, two dimensional, in the soil and bounds one side of a pedon. The pedon is the smallest three dimensional unit, but not less than 1 meter square on top, that captures the lateral range of variability.
While soil micromorphology begins in the field with the routine and careful use of a 10x hand lens, much more can be described by careful description of thin sections made of the soil with the aid of a petrographic polarizing light microscope. The soil can be impregnated with an epoxy resin, but more commonly with a polyester resin (crystic 17449) and sliced and ground to 0.03 millimeter thickness and examined by passing light through the thin soil plasma.
Porosityof topsoiltypically decreases as grain size increases. This is due to soil aggregate formation in finer textured surface soils when subject to soil biological processes. Aggregation involves particulate adhesion and higher resistance to compaction. Typical bulk densityof sandy soil is between 1.5 and 1.7 g/cm3. This calculates to a porosity between 0.43 and 0.36. Typical bulk density of clay soil is between 1.1 and 1.3 g/cm3. This calculates to a porosity between 0.58 and 0.51. This seems counterintuitive because clay soils are termed "heavy", implying "lower" porosity. Heavy apparently refers to a gravitational moisture content effect in combination with terminology that harkens back to the relative force required to pull a tillageimplement through the clayey soil at field moisture content as compared to sand.
Porosity of subsurface soil is lower than in surface soil due to compaction by gravity. Porosity of 0.20 is considered normal for unsorted gravel size material at depths below the biomantle. Porosity in finer material below the aggregating influence of
pedogenesiscan be expected to approximate this value.
Soil porosity is complex. Traditional models regard porosity as continuous. This fails to account for anomalous features and produces only approximate results. Furthermore it cannot help model the influence of environmental factors which affect pore geometry. A number of more complex models have been proposed, including
fractals, bubbletheory, crackingtheory, Booleangrain process, packed sphere, and numerous other models. [cite web|author=Horgan, Graham W. | year = 1996 | title = A review of soil pore models | type = PDF | url = http://www.bioss.sari.ac.uk/~graham/sprev.pdf | accessdate = 2006-11-03]
oil composition by laboratory methods
An experienced soil scientist can determine
soil texturein the field with decent accuracy, but not all soils lend themselves to accurate field determinations of soil texture. The mineral texture can be obfuscated by high soil organic matter, iron oxides, amorphous or short-range-order aluminosilicates, and carbonates. Soil texture is the relative relations of the components sand, silt and clay most often reported as percentages on a mass basis. Laboratory methods employ chemical pretreatments to mediate the effects of organic matter, iron oxides, amorphous or short-range-order aluminosilicates, and carbonates.
Wikimedia Foundation. 2010.
См. также в других словарях:
Soil science — is the study of soil as a natural resource on the surface of the earth including soil formation, classification and mapping; physical, chemical, biological, and fertility properties of soils; and these properties in relation to the use and… … Wikipedia
Soil classification — deals with the systematic categorization of soils based on distinguishing characteristics as well as criteria that dictate choices in use. Overview Soil classification is a dynamic subject, from the structure of the system itself, to the… … Wikipedia
Soil — For other uses, see Soil (disambiguation). A represents soil; B represents laterite, a regolith; C represents saprolite, a less weathered regolith; the bottommost layer represents bedrock … Wikipedia
morphology — morphologic /mawr feuh loj ik/, morphological, adj. morphologically, adv. morphologist, n. /mawr fol euh jee/, n. 1. the branch of biology dealing with the form and structure of organisms. 2. the form and structure of an organism considered as a… … Universalium
History of Soil Science — Justus von Liebig = The early concepts of soil were based on ideas developed by a German chemist, Justus von Liebig (1803 – 1873), and modified and refined by agricultural scientists who worked on samples of soil in laboratories, greenhouses, and … Wikipedia
overprinted soil — A soil in which new soil morphology has developed and is superimposed upon that of a pre existing soil due to a shift in pedogenic conditions such as a change in climate or hydrology; the composite morphology retains some relict features that… … Glossary of landform and geologic terms
Pedology (soil study) — Pedology (from Greek: πέδον, pedon , soil ; and λόγος, logos , study ) is the study of soils in their natural environment. [cite web |url = http://natres.psu.ac.th/Link/SoilCongress/bdd/symp45/75 t.pdf | title = Soil Preservation and the Future… … Wikipedia
International Union of Soil Sciences — The International Union of Soil Sciences (IUSS) founded in 1924, is a Scientific Union member of the International Council for Science (ICSU), which it recognizes as the coordinating body for the international organization of science. The purpose … Wikipedia
World Reference Base for Soil Resources — The World Reference Base for Soil Resources (WRB) is the international standard taxonomic soil classification system endorsed by the International Union of Soil Sciences (IUSS). It was developed by an international collaboration coordinated by… … Wikipedia
Glossary of plant morphology terms — Biologists that study plant morphology use a number of different terms to describe plant organs and parts that can be observed with the human eye using no more than a hand held magnifying lens. These terms are used to identify and classify plants … Wikipedia