Each soil tells a different story of its origins and management practices. On soilsmatter.wordpress.com, Eric Brevik at Dickson State University, North Dakota, points out that these differences are the result of five factors. He refers to them as ClORPT: climate, organisms, relief, parent materials and time.

Climate

  • Temperature and precipitation are the main factors making soils different from one another.
  • Precipitation dissolves minerals and salts in the soil. These move with the water down through the soil profile.
  • Climate and temperature also influences which plants and other organisms live in the soil.

Organisms

  • Animals and microorganisms living in soil decompose plant and animal tissues, and wastes. Eventually these become humus which influences soil color.
  • Organisms and humus also affect and the size and shape of the clumps of soil particles, called peds.
  • Peds are important because that is what makes a soil's structure.

Relief

  • Where a soil is found in the landscape relief or topography affects its characteristics.
  • Soils on slopes, for example, often experience more erosion and thus are shallower than soils on the top of a hill. Soils at the bottom of the slope are often much deeper due to the deposition of the eroded soil from the slope above.
  • A soil's position in the landscape can also indicate its inherent drainage (well, imperfect or poorly drained).

Parent materials

  • Soils develop from parent materials including minerals and rocks.
  • Some soils form directly over bedrock but others develop from the materials transported and deposited by glaciers, gravity, wind, rivers, lakes, or oceans.
  • These materials give soils their properties including particle size and minerals.
  • The minerals contribute color and influence chemical factors that affect pH and nutrient availability.

Time

  • All soil-forming processes take time.
  • Younger soils are typically shallower and often more fertile than older soils. It takes less time for a soil to form in sediments deposited by wind than from bedrock because plants can readily grow in sediments. Bedrock has to weather first into soil-sized particles.

As you look at different soils in a pit or a trench, think about how ClORPT factors gave them their character.

For other interesting posts about why soils matter visit: soilsmatter.wordpress.com.