Total organic matter is determined by heating dried and ground soil in a muffle furnace to a temperature where the organic matter burns off, leaving the mineral component of the soil. One check sample is included with each batch. Weighing and recording the location takes approximately two minutes per sample. The samples must be left in the oven overnight and cool for an hour in the morning. Approximately 5 g of dried soil are used for each sample.

Principle

Total organic matter is determined by heating dried and ground soil in a muffle furnace to a temperature where the organic matter burns off, leaving the mineral component of the soil.

Equipment

  • Thermolyne F-A1730
  • Ceramic crucible

Procedure

  • Soil should be dried, ground, and pass through a 2 mm sieve. It should be used immediately after being removed from a 100°C oven to ensure minimal water adsorption.
  • Weigh a crucible on the most precise balance available, and record the weight.
  • Add approximately 5 g of soil to the crucible and record the total weight.
  • Place the crucible in the furnace. Record the position of each crucible because chemical markings (Sharpie) will come off in the oven.
  • Close the furnace doors using the large lever on the left side of the oven.
  • Turn on the power switch and rotate the small wheel on the control box until it clicks and you hear a thump from below the oven.
  • Leave overnight.
  • In the morning, turn off the power and open the doors halfway. Wait a half hour.
  • Open the other door and wait another half hour.
  • Using gloves or crucible tongs, remove each crucible and weigh, remembering that position in the oven is how the crucibles are identified.
  • Record the new weight and calculate the percent mass loss of the soil. Assume all loss is organic matter.