Soil and soil components
Biological components of soil
It mainly occurs in waterlogged conditions. The C horizon, or soil base, includes the parent material, plus the organic and inorganic material that is broken down to form soil. The B horizon, or subsoil, is a dense layer of mostly fine material that has been pushed down from the topsoil. The U. Fusarium lini which causes wilt of flax Alasi secretes HCN, a deadly poisonous substance and Fusarium udum a fungus causing wilt of pigeon pea Arhar secretes fusaric acid in the roots of the host plants These toxic chemicals secreted by fungi may be responsible for causing wilt in the flax and arhar Cajanus cajan. The O horizon has freshly-decomposing organic matter, humus, at its surface, with decomposed vegetation at its base. Cycles of wetting and drying cause soil particles to be abraded to a finer size, as does the physical rubbing of material as it is moved by wind, water, and gravity. Roots of the higher plants take active part in the disintegration of rocky mass and also make the compact soil loose. Time Time is an important factor in soil formation because soils develop over long periods. Decomposition of dead organic matter: A number of soil microbes attack the dead remains of plants and animals and cause decomposition. Carbonic acid will transform calcite into more soluble calcium bicarbonate. Water contents above field capacity displace so much of the soil air that the plant roots usually suffer from inadequate aeration and serve to be detrimental. The identification of sand, silt, and clay are made based on size. Decomposers consume organic matter, water, and air to recycle raw organic matter into humus, which is rich in readily available plant nutrients. Materials are deposited over time, decompose, and transform into other materials that can be used by living organisms or deposited onto the surface of the soil.
Important group of soil organisms are given below Fig. Soil animals, including soil macrofauna and soil mesofaunamix soils as they form burrows and poresallowing moisture and gases to move about, a process called bioturbation. It is estimated that in soil micro flora bacteria form about 90 per cent of the total microbe population.
Singh, R. Steep slopes encourage rapid soil loss by erosion and allow less rainfall to enter the soil before running off and hence, little mineral deposition in lower profiles. This excess water is called gravitational water.
November 21, Image courtesy of FAO. Primary minerals, such as those found in sand and silt, are those soil materials that are similar to the parent material from which they formed.
Dead plants and fallen leaves and stems begin their decomposition on the surface.
Carbon dioxide and nitrogen also are important for belowground plant functions such as for nitrogen-fixing bacteria. Soft sediment deformation: Soil distribution is not the same at all depths.
What is soil
Often called [weathered granite], saprolite is the result of weathering processes that include: hydrolysis , chelation from organic compounds, hydration the solution of minerals in water with resulting cation and anion pairs and physical processes that include freezing and thawing. Beneath the C horizon lies bedrock. If soils remain waterlogged where gas is displaced by excess water , it can prevent root gas exchange leading to plant death, which is a common concern after floods. Soluble salts are not leached from these soils, and in some cases they build up to levels that curtail plant  and microbial growth. The identification of sand, silt, and clay are made based on size. Key Terms loam: soil with no dominant particle size that contains a mixture of sand, silt, and humus humus: a large group of natural organic compounds found in the soil composed of decaying plants and dead and living microorganisms Soil Composition Plants obtain inorganic elements from the soil, which serves as a natural medium for land plants. It moves in the direction where capillary tension is more. Although plants usually continue to absorb water in the soil drier than at permanent wilting stage, absorption is too slow to replace water losses and the resulting water deficit causes cessation of growth and finally results in death from dehydration. The parent material may be either created in its natural place or transported from elsewhere to its present location. Earthworms by the burrowing habit make the soil loose and fertile. Soil formation takes place over long periods of time. In semiarid regions, the lower effective rainfall on steeper slopes also results in less complete vegetative cover, so there is less plant contribution to soil formation. Actinomycetes prefer saline soils and soil bacteria grow fairly well in the neutral soils richly supplied with organic nutrients. Soil consists of these major components: Components of soil: The four major components of soil are shown: inorganic minerals, organic matter, water, and air. For all of these reasons, steep slopes prevent the formation of soil from getting very far ahead of soil destruction.
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