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Organic part of soil
Organic part of soil
SOURCES OF ORGANIC SUBSTANCE OF SOILS AND ITS FRACTIONAL AND GROUP STRUCTURE Primary sources of organic substances of the soil and biosphere are so-called primary producers, or autotrophs — the organisms capable to independent synthesis of organic substance from mineral compounds. In land ecosystems the overwhelming part of primary production is made by green plants. To the soil come not only fossils of the died-off plants (primary organic substance), but also products of their microbiological transformation, and also the remains of animals (secondary organic substance). Primary efficiency of various land ecosystems isn't identical and lies in limits: - from 1-2 t/hectare in a year of dry organic substance (different types of the tundra) to 30 - 35 t/hectare a year (damp rainforests) (see tab. 3). In agroecosystems to the soil comes the vegetable remains: - from 2-3 t/hectare a year (tilled crops cultures) - to 7-9 t/hectare a year (long-term herbs). Receipt of secondary organic substances of a microbiological origin has to be several times below primary efficiency, but can reach units of tons on hectare a year. Receipt of organic substances with the dying-off soil fauna doesn't exceed in the majority of types of soils 100-200 kg/hectare a year. In soils of various type nature of distribution of the arriving organic residues on a soil profile isn't identical. In forest cenosis the main part of primary production arrives with a land waste, while in grassy substantially with the died-off roots. It plays an important role in the subsequent transformation vegetable the remains and soil formation. The chemical composition of the fossils coming to the soil in many respects depends on type of the died-off organisms (table).
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