So many new terms

This last chapter in the soil and water class has included a lot of new terms and formulas. This is the “soil water” part of this semesters education. I feel that my head is a bit confused and to help my self and possibly some of you guys I am planning on organize and summarize  some of the new terms, which hopefully will help get clear before the exam this upcoming friday!


  • Bulk Density (g/cm3): The density of solids and porspace. Depends greatly on the mineral make up of soil and the degree of compaction. It is the weight of soil / volume. \rho = \frac{M_s}{V_t}
  • Porosity(%): measure of the open porspace in a soil (water or air). Porosity of surface soil typically decreases as particle size increases. \phi = 1-\frac{\rho_{\text{bulk}}}{\rho_{\text{particle}}}
  • Particle Density (g/cm3): the density of the solids. The particle density does not change like the bulk density does. ~2.65 g/cm3.
  • Soil Compressibility: Soils tendency to consolidate or decrease in volume. soil weight / bulk density. 
  • Soil Strength: Soil’s ability to resist deformation, functions of cohesive and frictional forces between soil particles.
  • Bearing Capacity: the capacity of soil to support the loads applied to the ground.

Macro Porspace – allows water to move through

Meso Porspace

Micro Porspace – ability to hold water in place


  • Adhesion = ability for water to attract to soil (or other element).
  • Cohesion = attraction between two water molecules. Hydrogen bounding. 
  • Gravitational = water that is moved through the soil by gravity. When saturated.
  • Soil Water Potential: amount of work that must be done per unit quantity of water from a pool of pure water to the soil water. It is the potential energy of water relative to pure free water (e.g. deionized water) in reference conditions. Measured in units of pressure, Bar. 

              Tension (-) Pressure (+)

Soil water classification:

  • Saturation – All porspace are full of water. Gravitational water is lost.
  • Field capacity – The maximum amount of water that a soil can hold, as by capillary action, before the water is drawn away by gravity.
  • Wilt point – defined as the minimal point of soil moisture the plant requires not to wilt.
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