Soil Colloids Flashcards
What are soil colloids?
The clay and humus particles in soil are referred to collectively as the colloidal fraction of the soil.
What is Humus?
Humus is the dark, organic material that forms in soil when plant and animal matter decay.
What are the 7 properties of colloids?
- Small size
- High specific surface
- Surface Charge
- Adsorption of cations
- Adsorption of anions
- Ion exchange capacity
- Relevant to the mobility of ions in the soil
What is the ion exchange capacity?
It is the measure of the number of cations/anions retained on the surface of soil particles.
What are the two types of clay?
Crystalline silicate clays and Non-crystalline silicate clays
What are the three types of soils where crystalline silicate clays are not found?
- Andisols
- Oxisols
- Histosols
Are most crystalline silicate clays positively charged or negatively charged?
Negatively charged
What are the two main non-crystalline silicate clays?
Allophane and Imogolite
What is the difference between tetrahedral sheets and octahedral sheets?
The tetrahedral sheet is a 4 sided building block composed of a central silicon ion surrounded by 4 oxygen atoms.
An octahedral sheet is an eight-sided building block of a central aluminum or magnesium atom surrounded by 6 oxygen atoms.
