Loss on Ignition (LOI)
Definition
Weight loss after heating dried soil to 550 degrees Celsius. Approximates the organic matter content. A simple, cheap, high-yield discriminator in field comparisons.
- Standard temperature
- 550 degrees Celsius
- What it measures
- Organic matter content in soil
- Standard method
- ASTM D2974
- Cost
- Simple and inexpensive
Common questions
How do you measure loss on ignition in soil?+
Heat a dried soil sample to 550 degrees Celsius, then record how much mass it loses. ASTM D2974 is the standard method. The weight that burns off approximates the organic matter content in the soil.
Why is LOI useful in forensic soil work?+
It's a simple, cheap test that gives reliable results for comparing soil samples in the field. Because different soils have different organic-matter content, LOI can discriminate between samples even when other properties look similar.
What does the loss in LOI actually tell you?+
The mass lost when soil is heated to 550°C is primarily organic matter burning away. The percentage of weight lost reflects how much decomposed plant, animal, and microbial material is in the soil. Higher loss means more organic content.
Related terms
- A Horizon
- The uppermost mineral soil horizon, darkened by organic matter accumulation and the layer most commonly transferred by footwear and vehicle contact.
- Chroma
- The saturation or colourfulness of the hue, from 0 (neutral grey) outward in whole-number steps. Strongly weathered, iron-oxide-rich soils have high chroma;...
- Clay Mineral
- A secondary phyllosilicate mineral produced by chemical weathering; includes kaolinite, illite, smectite, and chlorite, all diagnostic of parent material and weathering intensity.
- Density-Gradient Column
- Glass column filled with stepwise layers of liquids of decreasing density (commonly bromoform 2.89 g/cm3 and bromobenzene 1.50 g/cm3 mixed in known...
- Hue
- The dominant wavelength family of a colour, expressed as a position on the Munsell colour wheel. Soil hues run from 10R (red)...
- Munsell Chip Comparison
- The visual procedure of matching a soil sample against printed colour chips in the Munsell Soil Colour Chart under standard daylight conditions,...
- Munsell Notation
- A three-component colour code (Hue-Value/Chroma) standardised under ASTM D1535 for describing soil colour from the Munsell Soil Colour Chart.
- Munsell Soil Colour
- Standardised colour notation written as hue, value and chroma (e.g. 10YR 4/3 dark brown). Read by holding a moist soil sample against...
- Particle-Size Distribution
- The quantitative measurement of the proportions of gravel, sand, silt, and clay in a soil sample, determined by sieving and hydrometer or...
- Regur (Black Cotton Soil)
- Indian Vertisol formed on Deccan basalt. High in smectite (montmorillonite) clay, deep black colour, swells and shrinks dramatically with moisture. Major signature...
- Soil
- Weathered surface layer of earth made of mineral particles, organic matter (humus), water, air and living micro-organisms. The forensic interest is in...
- Soil Texture
- The relative proportions of sand, silt, and clay in the mineral fraction of a soil, expressed as a USDA or ISSS texture...
Explained in these topics
- Dust and Soil: Nature, Types and Forensic ExaminationWeight loss after heating dried soil to 550 degrees Celsius. Approximates the organic matter content. A simple, cheap, high-yield discriminator in field compar...
- Soil Composition, Classification and the Munsell SystemA method for measuring soil organic-matter content by heating a dry sample to 550°C and recording the mass loss; ASTM D2974 is the standard method.