If the demand of O 2 exceeds the supply, a thin oxidised surface layer, an mm thick or so, is formed. (c) For biological oxidation, such as oxidation of NH 4 + —N to NO 3-—N and S 2- and S° to SO 4 2. (b) In the chemical oxidation of ferrous iron (Fe 2+) and manganous manganese (Mn 2+) and (a) As an electron acceptor by soil micro-organisms in their cell respiration, Oxygen reaching the submerged soil surface is utilized in several ways: The thickness of the aerobic surface layer is determined by the ratio of O 2 supply from the atmosphere to the O 2 consumption in the soil.
#Submerge define free
The greater potential consumption of O 2 as compared to the available supply through the flood water results in two distinctly different layers being formed in a submerged soil: an oxidized or aerobic surface layer where O 2 is present and a reduced or anaerobic layer in which no free O 2 is present (Fig. Some O 2 trapped in blocked pore spaces is rapidly utilized by facultative anaerobic organisms. This rapid depletion of O 2 takes place within a day or so of submergence. The oxygen-diffusion in the water layer above the soil is very slow and the rate of O 2 consumption is reduced soil is high.īecause of this high demand of O 2 in submerged soil and slow O 2 supply through water, the soil is practically devoid of oxygen. Except in a thin layer at the soil surface, and sometimes a layer below the plough sole, most soil layers are virtually oxygen-free within a few hours after submergence.
When a soil is submerged, water replaces the air in the pore spaces. Diffusion of Molecular Oxygen and Development of Aerobic Anaerobic Layer : There are various changes like physical (depletion of oxygen, accumulation of carbon dioxide, compaction, bulk density, puddling, gaseous exchange and movement of water etc.), Chemical (soil reduction and transformation of different nutrient elements etc.), electro-chemical (soil pH, specific conductance and redox potential, Eh etc.) and biological properties (decomposition of organic matter mineralization and immobilization processes etc.) of soils that are strongly influenced by the soil submergence. Because as a result of soil submergence a variety of changes like physical, chemical, electrochemical and biological properties are modified of which majority of soil prosperities is suitable for rice cultivation. Soil submergence for rice cultivations is thus essential. In this system of rice cultivation, the production is very high. (ii) Wet-system, practiced in low lands or where irrigation is available.
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