Soil and Water Conservation Laboratory
Standard Operating Procedure
Loss on Ignition (LOI)
Reference Method: Wilke, Berndt-Michael,2005, ‘Determination of Chemical and Physical Soil
Properties,’ in Manual of Soil Analysis, Eds. Margensin, R. & F. Schinner, Springer, Germany,
pp. 74 – 76.
Purpose
To determine the soil organic matter of the soil of interest. The loss on ignition method is based
on based on ignition of a dried soil sample. The soil organic matter is calculated as the mass
difference before and after ignition (550 ± 25o C).
Methods and Equipment
 2-mm mesh sieve
 Drying oven, controlled at a fixed temperature of 105 ± 5o C
 Muffle furnace, capable of maintaining a temperature of 550 ± 25o C
 Analytical balance, accuracy 0.01g
 Porcelain crucibles or bowls
 Desiccator
 Gloves and thongs
 Protective eyewear
 Appropriate lab attire
Procedure
1. Use field moist, sieved (< 5mm) soil or air-dried (< 2mm) soil. Prior to LOI prepare the
soil sample by drying the soil to 105o C (refer to drying method as outlined in soil
moisture content or bulk density).
2. Next heat crucibles/ bowls in the muffle furnace at 550 ± 25o C for 20 minutes. Cool in
the desiccator and weigh (mc) to 0.1g.
3. Weigh 5 – 20 g of soil and put in the crucibles (m1). Then place crucibles with soil in the
cold muffle furnace.
4. Gradually heat the muffle furnace to 550 ± 25o C for 2 -4 hours until a constant mass is
reached.
5. Open muffle furnace door and cool to 100o C.
6. Remove crucibles and place in the desiccator and cool to room temperature (~ 1 hour).
7. Measure the mass of the crucible + ignited soil (m2) twice. The difference of the
individual measurements from the mean should not exceed 5%.
Calculation
1. Calculate the loss of mass after ignition at 550 o C (∆m; g):
m  m1  m2
2. Calculate the LOI which corresponds to the soil organic matter content:
1
LOI (%) 
m
 100
md
* Remember, md  m1  mc
∆m: loss of mass of the soil after ignition at 550oC (g)
mc: mass of crucible (g)
m1: mass of the soil dried at 105o C (g) and crucible
m2: mass of the soil ignited to 550o C (g) and crucible
md: mass of the soil dried at 105o C (g)
Example Calculation
mc = 3.11 g
m1 = 19.36 g
m2 = 16.77 g
1.
∆m = 19.36g – 16.77g = 2.59 g
2.
md = 19.36g – 3.11g = 16.25 g
LOI =
2.59 g
 100 = 15.94 %
16.25 g
2