pasado pls soils

• Soil

  A natural body originated from weathered (physical/chemical) rocks and minerals & decomposed organic matter, synthesized in a horizontal layer/profile

  
• Soil


  • Important in food production, base of infrastructures, and habitat of living organisms
  • Provides the basic needs of organisms and supports life on earth
• Types of Rocks


  • Igneous
  • Sedimentary
  • Metamorphic
• Igneous Rocks

  Originated from solidified lava or molten rocks, can be intrusive (solidified inside the volcano) or extrusive (solidified at the surface/ground)
• Sedimentary Rocks


  Formed from sediments (existing rocks, living organism, mineral particles) through processes of fragmentation, transportation, deposition, and cementation
• Metamorphic Rocks

  Formed due to high temperature and pressure, particularly in the mantle, subjected to "metamorphism"
• Types of Sedimentary Rocks

  • Clastic (made from clasts/fragments of previously existing rocks)
  • Biogenic (formed when a previously living organism was combined to inorganic compound)
  • Chemical (build up of minerals which dissolved in H2O)
• Types of Minerals

  • Primary (persist from original rocks)
  • Secondary (originated from chemical weathering of least resistant primary mineral)
• Soil Profile and Factors of Soil Formation
• Soil Texture


  Permanent property of the soil, can be changed through time via chemical weathering
• Soil Textural Classes


  • Sand
  • Loamy sand
  • Sandy loam
  • Loam
  • Silt loam
  • Silt
  • Sandy clay loam
  • Clay loam
  • Silty clay loam
  • Sandy clay
  • Silty clay
  • Clay

  
• Munsell Soil Color Chart


  A means to visually identify and match color using a scientific approach, with variables of Hue, Value, and Chroma
• Soil Structure


  The overall architecture of a soil defined by the assemblage of structural units, which it contains
• Types of Soil Structures

  • Granular and crumb
  • Blocky and subangular blocky
  • Prismatic and columnar
  • Platy

  
• Classes of Soil Structure

  • Very fine or very thin
  • Fine or thin
  • Medium
  • Coarse or thick
  • Very coarse or very thick

  
• Grades of Soil Structure

  • Structureless (massive or single-grain)
  • Weak
  • Moderate
  • Strong

  
• Soil Density and Porosity


  The liquid and gas portions are essential for plant growth and are found in the pore spaces among the soil solids

  
• Bulk Density


  A measure of the mass of a soil per given volume (i.e. g/cm3), including solids and pore spaces

  
• Particle Density

  A measure of the mass of soil solids per given volume (g/cm3), excluding pore space

  
• Soil material


  • Consists very largely of entire aggregates
  • Includes few broken ones
  • Includes little or no non-aggregated material

  
• Soil density


  Measure of the mass of a soil per given volume (i.e. g/cm3), including solids and pore spaces

  
• Soil porosity


  The percent by volume of a soil sample not occupied by solids

  
• The liquid and gas portions are essential for plant growth and are found in the pore spaces among the soil solids
• Bulk density


  Measure of the mass of a soil per given volume (i.e. g/cm3), including solids and pore spaces

  
• Bulk density is a commonly measured soil property by agriculturist and engineers
• High bulk density soils

  • Have little pore space
  • Water infiltration is reduced
  • Root penetration is inhibited
  • Aeration is restricted
  • Reducing agricultural productivity

  
• Low bulk density soils


  • Are easily compacted
  • May settle considerably to the detriment of roads, sidewalks, and building foundations

  
• Particle density

  Measure of the mass of soil solids per given volume (g/cm3), excluding pore space

  
• Particle density is approximated as 2.65 g/cm3, although this number may vary considerably if the soil sample has a high concentration of organic matter or high-density minerals

  
• Porosity


  The percent by volume of a soil sample not occupied by solids

  
• If particle density remains constant

  As bulk density increases, porosity decreases
• Loose, porous soils have lower bulk densities and greater porosities than tightly packed soils

  
• Porosity


  • Varies depending on particle size and aggregation
  • Is greater in clayey and organic soils than in sandy soils
  • A large number of small particles in a volume of soil produces a large number of soil pores
  • Fewer large particles can occupy the same volume of soil so there are fewer pores and less porosity

  
• Porosity does not tell us anything about the size of pores
• For an ideal soil, one-half of it is solids, and one-half is pore space

  
• Organic matter is a very small portion of the solids, so it is usually ignored in the bulk density calculation
• Compaction


  Decreases porosity as bulk density increases
• Aggregation


  Decreases porosity because more large pores are present as compared to single clay and silt particles that are associated with smaller pores

  
• Pore size


  • Pores come in all sizes, although clays have predominantly small pores, and sands have large pores
  • Most soils are a mixture of sand, silt and clay particles, so there is a mixture of different sized soil pores
  • An ideal soil condition is one with an equal number of large and small pores
  • Large pores allow for soil aeration
  • About 10 percent of the pores must be large enough for aeration so that root growth is not restricted
  • Small pores are connected to large pores that are connected to medium-sized pores
  • Within an aggregate, the pores are small, between aggregates, pores are large
  • Small pores are usually called micropores, and large pores are called macropores

  
• As organic matter is added


  The number of macropores increases