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Special PresentationsSoil fertility and soil examination F4Scheller, Edwin Kwalis GmbH, Fuldaer Str. 21, D-36160 Dipperz |
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| Most rocks and sediments contain primary silicates like feldspar and micas, which are rich in nutrients. During soil development primary silicates are weathered and their nutrients are liberated. Excretion of organic acids by plants and soil microbial biomass intensify weathering and liberation of nutrients. Carbon turnover to soil like root exudates and root residues influences most the amount of soil microbial biomass and also the mobilization activity for nutrients from soil minerals. Increasing intensity of agriculture and increasing crop yields intensify the weathering of primary silicates, the release of nutrients and the speed of soil development. For example potassium release ranges from 5 kg/ha x year up to 900 kg/ha x year, pinus forestry in comparison to sugar beets. N-supply of crops is one of the main influencing factors on assimilation, yield and carbon turnover to soil - and thus on the mobilization activity for nutrients. Crops with nitrogen deficency have also an energy deficency in rhizosphere. They are only able to take up soluble nutrients, but not to mobilize unsoluble nutrients. Normally 2/3 of nitrogen crops take up in conventional agriculture, are delievered from the humus N-reserve. Net-mineralization is influenced by carbon turnover to soil, the soil microbial biomass and can be additionally stimulated by green manure up to 10 kg N03-N/ha x day. Soluble potassium can be used as a guide element to asses the speed of transformation of primary silicates and the release of nutrients. Nitrate-nitrogen in the soil and soluble phosphorus often change during season every day. They are unsuitable for balancing nutrients. | |||
