Soil organic carbon (SOC) analysis involves determining the amount of carbon in soil's organic matter, typically measured as a percentage of soil dry weight, and can be calculated to estimate SOC stock (carbon per hectare) using bulk density and sampling depth.

 Soil organic carbon (SOC) analysis involves determining the amount of carbon in soil's organic matter, typically measured as a percentage of soil dry weight, and can be calculated to estimate SOC stock (carbon per hectare) using bulk density and sampling depth. 

Here's a brief breakdown:

1. Measuring Soil Organic Carbon (SOC) Concentration:

Methods:

SOC is commonly measured using wet oxidation methods like the Walkley-Black method, which oxidizes organic matter with potassium dichromate and sulfuric acid. 

Reporting:

The results are usually expressed as a percentage of total organic carbon (TOC) in the soil. 

Conversion to Organic Matter:

You can estimate soil organic matter (SOM) from SOC by multiplying the SOC percentage by a conversion factor (approximately 1.72). 

2. Calculating Soil Organic Carbon Stock (SOC Stock):

Formula: SOC stock (tC/ha) = (SOC% x soil mass (t/ha)). 

Soil Mass Calculation: Soil mass (t/ha) = bulk density (g/cm³) x sampling depth (m) x 10,000. 

Bulk Density: Bulk density is the mass of soil per unit volume, and it's crucial for accurate SOC stock calculations. 

Example: A soil with 1.3% SOC and a bulk density of 1.2 g/cm³ to a depth of 10 cm would have an SOC stock of 15.6 tC/ha. 

3. Key Considerations:

Gravel Content:

If the soil sample contains gravel, laboratory results need to be adjusted to account for it. 

Monitoring Changes:

Measuring SOC stocks allows for monitoring changes in soil carbon over time, which is important for understanding the effects of land management practices. 

Depth:

SOC is often measured to a depth of 0-30 cm, but deeper sampling can be beneficial for more accurate baseline estimates.