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Horticulture definition of soil composition
a mixture of rock, sand, loam, clay, humus and organic matter that is developed from the detritus of the decomposition of plant and animal materials and occurs as a top layer or horizon (as an aquitard) under the top layer of mineral soil. Soil is the basic ingredient of land and contains all the basic things necessary for the growth of plants and animals.
A layer or horizon of soil under another soil is usually of sand, and sometimes clay. The soil in the subsoil may be either homogenous, or have separate areas of different nature. Soil is a layer or layer of weathered rock, chiefly of sand or silt, or a more or less homogeneous combination of such material, sand or clay, sometimes with a well-defined horizon between it and the underlying mineral soil.
The fraction of sand or other mineral material, as compared with the fraction of organic matter, determines the fertility of soil, and whether it is classified as mineral or organic soil.
Three distinct types of soil are recognized: clay, loam, and sand. Sand is an inert mineral, being composed of silicates, alumina, iron, and some carbonate. Clay is a mineral or amorphous material that is composed of silicates, aluminosilicate, and alumina. The chief elements present in clay are iron, aluminum, magnesium, and sodium. The principal element present in sand is silicon. The clay minerals are hydrated aluminum silicate and potassium-magnesium aluminosilicate.
The fraction of sand in the soil is from 4 to 15 percent of the whole. Since sand is relatively stable, it is widely distributed in the earth's crust and is found in loose surface soils. In sand soil, the fraction of sand to sand and sand plus silt is usually 50 percent or more.
Loam soil contains more organic matter than sand and sand and silt. Loam is composed chiefly of calcium carbonate and feldspar, which are partly decomposable, and partly decarbonized, and derived from calcium and feldspars in the rocks. In loam there is a great variety of structure: fragments of sand, of clay, of pebbles, of fragments of quartz, of limestone, or of rock-cemented soil.
More clay than loam is found in the fine-loamy texture called sandy loam. It consists largely of particles of clay that are closely packed together. It has a brownish-gray or dark-gray color, and lightness that varies with the state of oxidation, with clay.
The soil under the subsoil is called subsoil or subsoil soil. It is composed of sand, clay, and sometimes silt. In a loamy subsoil, there is a fine gradation of particles from fine sand to clay and silt. The proportions of these particles in a loamy subsoil depend upon the fraction of sand or silt in the mineral soil above, and upon the relative immobilities of the constituents.
The shallow subsoil is composed chiefly of sand and clay. In this kind of soil, the sand fraction ranges from 15 to 35 percent and the clay fraction is from 4 to 17 percent. In a sandy subsoil, the sand fraction ranges from 15 to 35 percent and the clay fraction is from 10 to 30 percent. In a loamy subsoil, the sand fraction is less than 25 percent, and the clay is from 6 to 20 percent.
Soil has only the uses assigned to it by physics, chemistry, and biology, which are not increased by the addition of organic matter and are reduced by its decomposition. It is the ultimate destination of all the detritus of plant and animal life and its conversion into humus. In mineral soil, its benefits are further complicated by its secondary benefits, as permeability, durability, and other functions.
A sample of soil is a sample of rock that has been taken and analyzed, and from which the composition has been ascertained. In soil-soil relations, samples of soil are taken from one or more of the horizons below the surface of the mineral soil, usually in the topsoil.
Horizons of soil are physical or chemical properties that determine soil's function and importance for living organisms. They are defined as clear-cut, distinguished layers of different mineral and organic composition in a sand, clay, or loam horizon. These are found as layers or as an underlying and overlying layer of soil, and it can be a discontinuous layer.
The samples of soil are then characterized chemically and physically in soil-testing laboratories. Soil may be analyzed by chemical analysis, which is usually done in the laboratory, or by physical analysis, in which samples are examined by measuring or counting particles of the soil.
Пошто је земљиште крајње одредиште свих биљних и животињских отпадака, биљке и животиње у тлу чине еко-биосферу. Еко-биосфера је биосфера на коју утиче активност земљишта. Зона која је граница између тла и минералног земљишта назива се подземље. Утицај тла или подземља на минерално земљиште одређује да ли је класификовано као минерално или органско земљиште.
То је тло које је под утицајем вегетације. У току живота биљке таложи лишће, распада биљну материју и распада животињску материју на површини земљишта.