Controlled largely by the parent rock. It controls the colour, nutrients quality, ph of the soil and drainage properties.
The 4 things that make up soil
air
rocks/minerals
organicmatter
water
The inputs of soil
gases from atmosphere
precipitation
nutrients from parent rock
organicmatter from decay of organisms
Outputs of soil
soil erosion
evapourtranspiration
leaching of the soil
What system are soils?
Soils are an open system.
Stage 1: Weathering
Weathering breaks apart the parent rock into pieces and forms the regolith
Clay particles join together (process of aggregation)
Stage 2 : Colonisation/humification
Once the rock has been brokenapart, organisms such as algae/ lichens can start to colonise the area, and then add organic matter to the soil when they die.
Role of earthworms in the soil
break organicmatter into smallerpieces
mix and aerate the soil
increase the soul pH
improve the soil stucture
What is the humification?
Process by which dead organic matter is decomposed to form humus.
Chelation
As the organic matter decomposes, it releases nutrients and organic acids, these acids attack clays releasing iron and aluminium
Stage 3 : Translocation
Movement of soilcomponents in any form or in any direction
Occurs with greatest effect with either very high or very low rainfall.
Most common in tropical or desert climates
Leaching
Common in areas of intense high rainfall.
It is the carrying of elements in a dissolved form.
What is leaching controlled by?
Solubility of an element
The more soluble a mineral is the greater is suspectibilty to leaching
Rainfall
Leaching becomes more rapid as the percolating water becomes more acidic.
Parent rock material( factors affect formation of soil)
Controls
soil colour, therefore temperature
mineral component
soil texture, which affects the drainage of the soil
soil depth
Climate( factors affect formation of soil)
Climate affects the rate of weathering.
In hot arid climates, high temperatures draw moisture up to the surface.
This is called salinisation.
Topography( factors affect formation of soil)
Precipitation increases with altitude but temperatures decrease.
Valleyfloors have deeper soil due to soil creep downwards
Add organicmatter when they die. Humicacid are released during decomposition and may break down the clays.
Worms:
mix and aerate the soil.
Fungi/bacteria
assist in decomposition and decay of dead vegetation which releases humicacids to the soil. The bacteria can also fixnitrogen and assist in nitrification of the soil.
Time( factors that affect formation of soil)
The longer the soil has to form, the greater the weathering and organic matter breakdown; meaning deeper soils to support a higher species diversity
Soil organic matter practical (Step 1)
Use the dry sample of soil, place the crucible with soil onto the tripod and clay pipe triangle above the bunsen burner
Soil organic matter practical (Step 2)
Light bunsen burner and heat the sample, maintain a red glow on the crucible for 30 minutes
Soil organic matter practical (Step 3)
Allow to cool
Soil organic matter practical (Step 4)
Measure the mass of the crucible with the burned soil
Soil organic matter practical (Step 5)
Use the equation below to calculate soil organic content as a % of dry mass
Soil organic content as % of dry mass= ( C - D ) / ( C-A ) X 100
Soil compaction practical (Step 1)
Hold the knitting needle perpendicular to the ground at a height of 1metre and let go
Soil compaction practical (Step 2 )
Hold the knitting needle at the surface of the soil
Soil compaction practical (Step 3)
Pull out from the soil and measure the length of knitting needle ( mm ) that was in the soil