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Manganese Cycle. Foliar sprays (usually MnSO 4 ). Deficiencies pH>7.0, <20 ppm Toxicities pH<5.5, >500 ppm Optimum availability at pH 6.2 to 6.4. Fertilizer and Manure. residue. Plant uptake. diffusion. Parent material. Precipitated Mn oxides. > pH 7.0. Organic complexes
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Manganese Cycle Foliar sprays (usually MnSO4) Deficiencies pH>7.0, <20 ppm Toxicities pH<5.5, >500 ppm Optimum availability at pH 6.2 to 6.4 Fertilizer and Manure residue Plant uptake diffusion Parent material Precipitated Mn oxides > pH 7.0 Organic complexes (predominantly soil organic matter) Mn2+ exchangeable (adsorbed cation or in solution) Biological oxidation Bacteria - Arthrobacter, Bacillus Fungi - Cladisporium, Curvularia weathering oxidation reduction reactions Mn4+ as MnO2, very inert oxide generally at pH > 8.0 Mn3+ as Mn2O3, unstable oxide