Question

The organic matter is calculated by multiplying the organic carbon value by a conversion factor _______ on the assumption that soil organic matter contains 58 per cent carbon.

• A. 1.724
• B. 1.247
• C. 1.110
• D. 1.234

Hint:

Although modern research shows the carbon content of organic matter varies between \(50\%\) and \(60\%\) across different soil types, \(1.724\) remains the standard textbook conversion factor in soil science.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Soil organic matter (SOM) is composed of carbon, oxygen, hydrogen, nitrogen, and other trace elements. Analytical methods usually measure soil organic carbon (SOC) directly, which is then converted to estimate total organic matter.
Key Formula or Approach:
Assume that soil organic matter contains \(58\%\) carbon by weight: \[ \text{Soil Organic Matter} = \frac{\text{Soil Organic Carbon}}{0.58} \] \[ \text{Conversion Factor} = \frac{1}{0.58} \approx 1.724 \]

Step 2: Detailed Explanation:
The value \(1.724\) is known as the Van Bemmelen factor.
To estimate the total organic matter content of a soil sample, the measured organic carbon percentage (often determined via the Walkley-Black wet oxidation method) is multiplied by this conversion factor.

Step 3: Final Answer:
The conversion factor is 1.724.