Soil organic matter content is one of the important indicators for measuring soil fertility. Therefore, its measurement is of great significance for soil fertility regulation in actual production. So, what are the methods for measuring soil organic matter content? The specific methods are as follows:
1. TOC Analysis
The organic carbon in the soil sample was burned at a high temperature of 1100 degrees Celsius to release carbon dioxide. The resulting TOC value was then collected using a high-sensitivity detector. The TOC value multiplied by a coefficient of 1.724 gives the organic matter content in the soil.
2. Potassium dichromate titration method
A soil solution containing potassium dichromate oxidant and sulfuric acid was boiled in an oil bath at 170-180°C for 5 minutes. The carbon in the soil organic matter was oxidized to carbon dioxide by potassium dichromate, while the hexavalent chromium in the potassium dichromate was reduced to trivalent chromium. The remaining potassium dichromate was titrated with a standard solution of divalent iron. Based on the amount of ferrous sulfate consumed by potassium dichromate before and after the oxidation of organic carbon, the content of organic carbon was calculated, and then the content of soil organic matter was calculated.
3. Hydration heat colorimetric method
K2Cr2O7 and concentrated sulfuric acid were added directly to the soil sample. The heat generated by the rapid mixing of concentrated sulfuric acid and potassium dichromate solution (temperature around 120℃) was used to oxidize the organic carbon in the soil. The organic carbon content of the soil was determined by the change in the green chromium ions (Cr3+) produced after reduction in the soil solution or the orange color of the remaining potassium dichromate.
4. Ultraviolet spectrophotometry
By utilizing the unique ultraviolet absorption characteristics of soil organic matter, the content of organic matter can be estimated by analyzing the absorbance of the soil solution in the ultraviolet spectral range.
5. Alkaline hydrolysis method
Soil samples are subjected to an alkaline hydrolysis reaction with sodium hydroxide or potassium hydroxide solution, converting organic matter into organic acid salts in the solution. The organic matter content can be calculated by measuring the concentration of these organic acid salts.
