Moorland Indicators of Climate Change Initiative
Calculating the carbon content of a soil sample
Introduction / Rationale
Peat soils have a high soil organic matter (SOM) concentration an therefore store
high amounts of carbon.
The "loss on ignition" test allows the organic content of sediments to be calculated.
The standard procedure is based on Avery and Buscomb (1964) and involves
prolonged exposure to high temperatures (thus burning all of the organic material
and leaving only the minerogenic component). Loss on ignition should be performed
on samples that have already been subject to moisture content analysis, to give a set
of comparable data.
Method
Roughly 5 grams of each dried and sieved sample produced during moisture content
analysis is placed in a ceramic crucible and subjected to a high heat.
1. Weigh a clean, dry, porcelain crucible (to 0.01g).
2. Take sediment sub-sample and oven dry at 35ºc for 24 hrs. Crush soil to powder
form.
3. Add 5g of oven dry, crushed soil to crucible. Reweigh and record weight.
4. Heat for 5mins at 110ºC to drive water off.
5. Place samples in muffle furnace at 550ºc for 4 to 4 ½ hrs.
6. Or blast with one or more Bunsen burners for as long as possible.
7. Allow oven to cool and then remove samples from muffle furnace.
8. Heat for 5 mins at 110ºC again. Remove and weigh immediately.
9. Using the following equation work out organic percentage
100-[ { (‘weight after burning’ – ‘weight of crucible’ ) / (‘weight before burning’ – ‘weight of
crucible’) } X100]
Equipment required
Measuring scales
Crucibles
Use of a muffle furnace or Bunsen burners
Extra challenge:
Can you work out how much soil carbon is store in a m³ peat? How much would this
be in the top layer of your 30m2 moorland at the depths you measured?