Soil organic matter

DOM is an acronym for the dissolved organic matter in the soil (English: dissolved organic matter). By definition, the molecular size must be less than 0.45 microns, otherwise it is called particulate organic matter. A distinction is dissolved organic carbon (DOC), dissolved organic nitrogen (DON), dissolved organic phosphorus (DOP) and dissolved organic sulfur ( DOS). The DOM is localized mostly in the organic layer, especially in the Oh horizon. Approximately 10 to 30% reach the mineral soil, or are formed there.

Components

DOM consists of humic and fulvic acids, as main components, as well as amino acids, carbohydrates, fatty acids. In addition, you count to organic metal complexes and clay-humus complexes, where these are less than 0.45 microns. Living components of DOM are viruses. Microorganisms are usually too big and therefore play no role.

Extraction

The DOM can in principle be obtained in two ways, on extraction method and lysimeters or suction cups. In an extraction in the laboratory to Win an equilibrium solution with lysimeters / suction cups the entire soil solution. Depending on the process results in a DOM of different quality and quantity.

Genesis

By (micro) biological activity of the potential DOM is first formed from the solid organic substance. Then solves this by hydrological and physicochemical processes, creates the DOM.

Factors

There are multiple factors that influence on the DOM Education:

  • PH: A high pH, the DOM formation is supported because the hydrophilicity by a higher OH - dissociation increases.
  • Metal ions: More metal ions lead to increased complexation associated with precipitation and therefore less DOM.
  • Temperature: As temperature increases, increases the DOM education because the solubility and microbial activity increases.
  • Water content / flow: Through higher water content and higher flow can more organic matter ( DOM potential ) are dissolved.
  • Temperature and humidity dynamics: Both frost -thaw, and drying out rewetting cycles increase the availability of organic matter (aggregate destruction, dead microbial biomass ), thus reinforcing the DOM education.

Furthermore, for example, the carbon-nitrogen ratio, the redox potential or ionic strength influence the formation of dissolved organic matter.

Source and drain in the bottom of

Among the sources of DOM include humus, litter, root exudates and microorganisms. Scattering and the resulting humus have a large root exudates of only minor importance. In the case of microorganisms one is so far only in terms of the qualitative Relevance agree. At which point they play a role in the discussion.

Possible sinks in the soil leaching, ie the effluent from the bottom in deeper layers, groundwater or surface water, the degradation by microorganisms and adsorption to soil particles. Degradation is usually supported by adsorption to surfaces. Moreover, organic substances are accumulated in the soil matrix by adsorption.

Importance

DOM is significant in the nutrient cycles ( of carbon, nitrogen, phosphorus, sulfur), as it is a moving group. It is a substrate for microorganisms and may be taken up by plants. With the DOM partly pollutants are mobilized, transported and made ​​bioavailable. Also plays a role in the DOM of podsolization.

  • Soil Science
Vomitoxin Podzolization
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