what is soil ?what are the factors contribute to soil formation?
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Answer:
The upper layer of earth in which plants grow, a black or dark brown material typically consisting of a mixture of organic remains, clay, and rock particles.
Soils are formed through the interaction of five major factors: time, climate, parent material, topography and relief, and organisms.
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Soils are formed through the interaction of five major factors: time, climate, parent material, topography and relief, and organisms. The relative influence of each factor varies from place to place, but the combination of all five factors normally determines the kind of soil developing in any given place. In Plymouth County parent material and relief as it relates to drainage, account for many of the differences among the named soils. The following are brief explanations of the factors contributing to soil formation in Plymouth County Massachusetts.
Time:
The formation of soils is a continuing process and generally takes several thousand years for significant changes to take place. The soils of Plymouth County began to develop immediately after the ice retreat of the last glaciation (Pleistocene), approximately 14,000 years ago. The soils are considered to be relatively young soils with slight alteration of parent material and weak soil horizon development. Most of the soil orders mapped in Plymouth County are Inceptisols, Entisols, and Spodosols.
Climate:
Climate, particularly temperature, precipitation and frost action have a profound influence on the soil forming processes which occur within a region. The kind of climate largely determines the nature of the weathering processes that will occur and the rates of these chemical and physical processes. It directly affects the type of vegetation in an area which in turn will affect those soil forming processes related to vegetation. Plymouth County is in a transitional climate zone with conditions characteristic of both humid marine and humid continental climates. The winters are quite mild for New England due to the moderating effect of the surrounding Atlantic waters.
Parent Material: Link to General Geology of Plymouth County, Massachusetts
Parent material is the unconsolidated mineral and organic deposits in which soils are developing. It determines the mineralogical composition and contributes largely to the physical and chemical characteristics of the soil. The kind of parent material also influences the rate at which soil forming processes take place.
Organic deposits are accumulations of plant materials of varying degrees of decomposition that have formed in wet areas and are 16 inches or greater in thickness. The Freetown and Swansea soils developed in freshwater organic deposits. The Ipswich and Pawcatuck soils developed in organic tidal marsh deposits.
Alluvial deposits are recent material which has been deposited by flowing water. Alluvial deposits occur along the major rivers of the country .
Topography and Relief
The shape of the land surface, its slope and position on the landscape, greatly influence the kinds of soils formed. In Plymouth County soils that formed in similar parent materials with the same climatic conditions exhibit differences as a result of their position on the landscape. These differences are largely a result of varying drainage conditions due to surface runoff or depth to water table.
Soils that developed on higher elevations and sloping areas are generally excessively drained or well drained. Depth to groundwater is generally greater than 6 feet and surface runoff is moderate or rapid. Soil profiles within these areas commonly have a bright colored strong brown to yellowish brown upper solum grading to a lighter, grayer, unweathered substratum.
Organisms
All living organisms actively influence the soil forming process. These organisms include bacteria, fungi, vegetation and animals. Their major influence is the effect on the chemical and physical environment of the soils.
Most, if not all of Plymouth County, was originally in native forest of mixed hardwoods and conifers in varying proportions. The mineral element content of leaves and branches varies depending on the type of forest vegetation, and influences the characteristics of the soils that develop beneath it. Hardwoods characteristically take up bases (calcium, magnesium, and potassium) from the soil and return them to the soil surface in the form of organic litter; thus recycling the soil nutrients. Coniferous trees tend to be low in bases, consequently soils developed beneath them tend to be more acid. Bases are also more susceptible to leaching beneath coniferous trees. Mixing of the soil, due to tree throws, is also a characteristic of woodland soils.