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Concentrations of manganese in terrestrial plants tend to range from 20 to 500 mg/kg dry weight. Members of the Ericaceae family, which includes blueberries, are regarded as manganese accumulators. There are numerous reports of foliar manganese levels in excess of 2,000-4,000 mg/kg.

Mean manganese concentrations in bird´s eggs from a variety of geographical areas range from 1 to5 mg/kg dry weight, mean liver concentrations range from 3 to 11 mg/kg dry weight, and mean feather concentrations reach from 0.3 to 40 mg/kg dry weight. Mean manganese concentrations of up to 17 mg/kg dry weight have been found in tissues (liver, kidney and whole body) from a variety of reptiles and wild mammals.

 

Manganese is an essential nutrient for micro-organisms, plants and animals. Nutritional manganese requirements for terrestrial plants are around 10 - 50 mg/kg tissue. Critical nutritional levers vary widely between species and among cultivars of a species. Calcareous soils, especially those with poor drainage and high organic matter, are the types of soils that produce manganese deficient plants. Symptoms of manganese plants vary widely with species and include marginal chloroses, necrotic lesions and distorted development of the leaves. Toxic manganese concentrations in crop plant tissue vary widely, with critical values ranging from 100 to 5,000 mg/kg. Manganese toxicity is a major factor limiting crop growth on acidic, poorly drained, or steam-sterilized mineral soils. There is a wide range of variation in tolerance to manganese between and within plant species.

 

Summary

 

Manganese is present in soil as a result of mineral weathering and atmospheric deposition, originating from both natural and anthropogenic sources. There are three possible oxidation states of manganese in soil: , namely Mn(II), Mn(III), and Mn(IV). The divalent ion is the only form that is stable in soil solution, while Mn(II) and Mn(IV) are only stable in the solid phase of soil. Manganese mobility in soil is extremely sensitive to soil conditions, such as acidity, wetness, organic matter etc. The solubility of soil manganese is thus controlled by redox potential and soil pH, where low pH or low redox potential favour the reduction of insoluble manganese oxides resulting in increased manganese mobility. At soil pH above 5,5, manganese forms bonds with organic matter, oxides and silicates whereby its solubility decreases . Manganese availability is thus generally low at high pH and high organic matter content, while in acid soils with low organic matter content its availability is high. The solubility of manganese is also high in anaerobic conditions at pH above 6, as well as in aerobic conditions at pH below 5.5 aerobic conditions at pH above. That means, the bioavailability depends from the solubility and from the degree of dissociation. The manganese di(acetat) is the only compound in the group of soluble inorganic manganese compounds which react weak like a base (weak alkaline), in the meanwhile the other members (sulphate, chloride, nitrate) react like an acid. This could be the explanation for the fact that manganese di(acetate) does not have any bioaccumulating properties under test conditions.

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