Soil Physical Properties Flashcards
What is soil physics?
It is the understanding of how solids, water, and air in the soil interact with each other.
Why do we care about the physics of the soil?
To ensure the continuity of the ecosystem services the soil lends to us. (Provision, regulatory, cultural support, etc.)
What is soil matrix?
They are the solid particles in the soil that give it structure. This includes the parent material and the organic matter.
Why is the soil matrix important?
It determines the geometric characteristics of the pores in which water and air are transmitted and retained.
What are 6 examples of soil characteristics derived from color?
- Identify soil classification
- Distinguish soil horizons
- Waterlogging conditions
- Drainage class
- Warm reddish color: Tropical and subtropical zones
- Black and grey: Temperate zones
What is the biggest particle that is considered soil?
2mm
What are 3 factors that influence soil color?
- Organic Matter
- Water content
- Presence and oxidation states of iron and manganese
What are the 5 principal hues in soil?
Red, Yellow, Green, Blue, and Purple.
What are the three soil color characteristics using the Munsell Soil Color chart?
- Hue (Basic color)
- Chrome (brightness)
- Value (Shade)
What does 0 and 10 value mean?
0 = Black
10 = White
What is the most used property to characterize the solid phase of the soil?
Soil Texture
How can you measure soil texture qualitatively vs. Quantitatively?
Qualitatively: Through the feel of soil
Quantitatively: Measuring the ratio of different sized particles.
What is the range in particle size of sand?
2mm - 0.05mm
What is the range in particle size of silt?
0.05mm - 0.002mm
What is the range in particle size of clay?
0.002mm - 0.0002mm
What are the two methods of determining soil texture in the lab?
- Dispersion of the soil sample in an aqueous solution to separate the primary particles.
- Separation of the particles into size groups.
What are the three limitations to Stokes Law?
- Not all particles are spherical
- The soil particle mass is average and some particles can be heavier or lighter.
- Increasing temp decreases density and viscosity of water.
Briefly explain the Pipetting method.
For this method, you pipet different samples from a beaker of soil and water solution. Pipet solutions at different time intervals and different heights to reveal particle size.
Briefly explain hydrometer method.
A hydrometer is used to measure relative density. The test tube with more water separated is less dense.
What is the deflocculation process?
It is the process of separating soil particles.
Why do clay soils need to dry for a much longer period of time?
Because they retain water very well.
What are the 6 stoke’s law assumptions?
- The particles are small enough to be unaffected by the random movement of water molecules.
- The particles are rigid, spherical and smooth
- The particles have the same density
- The suspension is sufficiently dilute and dispersed that particles do not interfere with one another and each settles independently.
- Fluid flows around the particles in laminar not turbulent.
- Fluid density and viscosity are constant during the settling period.
Briefly describe single grained soil structure.
Soil particles are not attached at all. Ex: Dessert sand
Briefly describe massive soil structure.
Soil particles are tightly packed.
Ex: Dry Clay.
Briefly describe aggregate soil structure.
Soils that are ideal for farming. Particles are associated with small clots known as aggregates or peds.
