Summary
Soil carbon analysis measures the amount of carbon in soil using various methods, which is vital for understanding soil health, fertility, and its role in the global carbon cycle. Testing soil carbon helps farmers improve soil productivity and supports climate change mitigation through carbon sequestration. The loss on ignition method is a cost-effective and simple technique for determining soil organic carbon content, aiding sustainable farming and environmental management.
What is soil carbon analysis?
Soil carbon analysis is the process of measuring or determining the amount of carbon present in the soil. This process can be achieved by various methods, ranging from chemical analysis, physical analysis, or biological analysis. The choice of either of the methods depends exclusively on resource availability, the experience of the researcher, the needs of the study, or the level of accuracy needed. Soil carbon analysis is crucial because soil carbon plays a crucial and fundamental role in soil health, fertility, and physical conditions. Soil carbon is also a significant contributor to the global carbon cycle. Understanding the amount and distribution of soil carbon is crucial in understanding the impact of land use practices and management on soil health and fertility, and the best ways of enhancing soil carbon sequestration capacity purposefully for climate change mitigation and opportunities for carbon trading.
Why test for carbon in soil?
Climate change is a contemporary global environmental issue of concern. Therefore, we urgently need to work extra hard to enhance soil, tree or other vegetation's carbon sequestration. Governments such as the Irish have developed a plan to compensate farmers who add more carbon to the soil. It is therefore one way of enhancing the farmers' livelihoods through revenue. Testing for soil carbon will also help farmers understand their land's health and fertility and what measures they need to correct any soil deficiency for farm productivity enhancement.
Who is Soil Carbon analysis recommended for?
- Farmers
- Research centres
- Agricultural consultants
- Foresters
What is the process for soil carbon analysis?
Soil collection
Soil samplings are collected from a specific location at different depths of the soil profile using either a soil auger or sore core and taken to the laboratory for analysis.
Soil carbon detection
Various methods can be used to detect soil carbon. The main methods are Walkley Black and loss on ignition. The former method is preferred for its accuracy and precision.
Data analysis
The analysis results can be reported as the soil organic carbon content, usually expressed as soil weight or volume. Understanding soil health, fertility, and soil organic matter is essential for making decisions and implementing other farm management practices.
Interpretation
The findings can provide valuable insight into soil quality, nutrient cycling, microbial activity, and the potential for carbon sequestration. They can guide farmers in making informed decisions about soil management practices and the best ways of promoting sustainability in production. They can also help environmental scientists understand the impacts of various land management practices on soil carbon content.
Example: Soil carbon analysis using the loss on ignition method
Soil sampling collection
Soil can be collected at various depths of a soil profile using a soil auger. The soil will be collected from the four corners of the land and from the middle. This is to ensure that all the soil from the land under study is cared for. The first soil collected from a depth of 0-5cm will be discarded as it is assumed to contain mostly organic matter and other undecayed materials. The soil will be collected at a depth of 6-10cm,11-14 cm, and then put in a soil bag and taken to the laboratory for soil carbon analysis
Laboratory analysis
- Fresh soil weight is recorded as bulk density.
- Soil is dried at about 106 °C to remove moisture, then weighed again.
- The dry soil is ignited at 550 °C for 4-6 hours and reweighed.
Determination of the soil carbon content
Step 1. Calculation of organic matter
Formula: OM (%) = W1-W2 x100
W1
Where OM is organic matter, W1 = the weight of dry soil before ignition,
W2 weight of the soil after ignition at 550 degrees Celsius (g)
Step 2. Conversion of organic matter into soil organic carbon
SOC% = OM%X CF (0.58)
Where CF is the conversion factor (0.58) since organic matter is roughly 58% of carbon (however, the CF can slightly vary with the soil type, e.g., from 0.50 to 0.60)
Step 3. Calculation of soil carbon sequestration (Mg C/ha)
Soil C (Mg C/ha) = (SOC%/100 x Bulk density (g/cm3) X Soil Depth(cm) x 10
This process can be repeated for soils under different farming systems to compare carbon sequestration, such as agroforestry versus conventional cassava farming. The method is cost-effective and saves time and resources.
