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Soil Organic Matter Determination

Soil Organic Matter Determination. Soil organic matter quantity - Can be express ed as a percentage - Can be express ed as mg.g -1 The wet oxidation of SOM using acid dichromate (K 2 Cr 2 O 7 ) is followed by the potentiometric titration with ferrous ammonium sulfate – Tjurin method

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Soil Organic Matter Determination

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  1. Soil Organic Matter Determination • Soil organic matter quantity - Can be expressed as a percentage - Can be expressed as mg.g -1 The wet oxidation of SOM using acid dichromate (K2Cr2O7) is followed by the potentiometric titration with ferrous ammonium sulfate – Tjurin method • Soil organic matter quality - Can be evaluated by C:N ratio - Can be evaluated by Humic acid and Fulvic acid ratio Measuring of soil extract absorbance

  2. SOM Quantity Determination • Grind the soil and sieve it through 0.25 mm sieve • Weight 0.3 g into 100-150 ml beaker • Add 10 ml of K2Cr2O7 into the beaker • Stir the soil with K2Cr2O7 carefully • Cover the beaker using the watch glass • Insert the beaker into the oven (125°C) for 45 min. • Wash the beaker side and watch glass using distilled water • Titration with (NH4)2Fe(SO4)2

  3. Tjurin method Equation 2 K2Cr2O7 + 8 H2SO4→ K2SO4 + 2 Cr2(SO4)3 + 8 H2O + 3 O2 3 O2 + 3 C → 3 CO2 K2Cr2O7 + 7 H2SO4 + 6 Fe(NH4)2(SO4)2→ K2SO4 + Cr2(SO4)3 + 3 Fe2(SO4)3 + 6 (NH4)2SO4 + 7 H2O Acid dichromate Mohr salt

  4. Calculation • Factor of Mohr salt • Cox • Humus content . .. .

  5. Evaluation of Cox/Humus Content

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