5.1 Intro to Soil Systems and Society

Soil is made of rock particles, humus (organic matter made from the decomposition of living matter), water, air, and soil organisms that break down large particles, decompose, while mixing and aerating soil.

Soil is used for root growth and uptake of nutrients and water, habitat for organisms, filters water often changing its chemistry, store and transfer heat, and recycling nutrients. Soil is considered a system

Soil is typically a 50:50 mix of solids and pore spaces. The pore spaces contain a mix of air and water. Soil is made through weathering of rock, the decomposition of sediments by erosion, and the decomposition of organic matter. It is a very slow process that can take centuries. Three components of soil:

  1. Clay

  2. Silt

  3. Sand

If equal portions of each are present it is defined as a loam.

O Horizon: newly added organic material, comes from organisms that die and end up on top of the soil

E Horizon: (Zone of Leaching) subsoil horizon showing depletion of organic matter and minerals. Leaching occurs when precipitation>evaporation.

A Horizon: (Humus layer) decomposing organic matter often mixed with fine mineral particles

B Horizon: Sub soil, this is the layer where soluable minerals like clay, iron, and sats and organic matter tends to be deposited from the layer above.

C Horizon: this layer is mainly weathered rock from which soil forms

R Horizon: Hard bedrock

Permability: the rate at which air and water can flow through the layers

Porosity: the space between the particles

Clay soils encourgae high acidity. As the soil absorbs more water, clay particles begin to fill up with H+ ions. This binds soil water tightly to the clay aprticles and makes the soil more acidic. However, ti also reduces the availablity of other positive ions that can bind, allowing potassium, magnesium, adn ammonium to be lost to leaching. Acidic soil also increase the availability of aluminum and iron—which are toxic to plants.

—> Acid rain caused by industrial pollution has made soil inNorthern Europe more acidic.

Fertile soil is considered a non-renewable resource.