Chapter 14 Soil Formation/Properties GEOL 215

Grain/particle Size

Classified using sieves

Gradation

Distribution of particle sizes in soil.

Effective size

Grain size corresponding to 10% passing on a grain size distribution curve

Well-graded soil

Having good representation of particle sizes from largest to smallest

Uniformly graded

primarily particles of the same size

Gap Graded

Contains large and small particles, nothing between

Grain shapes

Bulky (same in 3 dimensions)

Platy (thin, mica)

Needlelike

Three-phase composition

Soil particles (solids), water, and air

Soil pH

Buffered with minerals Calcite (CaCO3) or Gibbsite (Al(OH)3) that consume H+ protons, when they dissolve and release H+ when they precipitate, they buffer pH. Determined by leaching that removes Ca2+ from soil. Lime increases pH

Radon

colorless, odorless radioactive gas in radioactive decay of uranium rocks and soil, causes lung cancer, common basalt

Macronutrients

Carbon, Hydrogen, oxygen, nitrogen, phosphorous, potassium, sulfur, calcium, magnesium