1. Soil Structure
Action movie

2. Soil Texture
Mineral Portion of Soil is made up of 3 different sized particles
Most soils are a mixture of these, therefore a soils texture depends on the relative proportions of sand, silt, and clay particles.
Most soils also contain larger
particles, but those aren’t
considered in a soils texture

3. Soil Texture Finger Test Moisten soil and rub it between your fingers
Sandy soils are gritty and fall apart easily
Silty soils feel a little slippery like baby powder
Clay soils feel sticky and can be rolled into a ball easily
Loam: Soil that has fairly equal proportions of sand, silt, and clay
Ideal for agriculture
Sand particles provide good drainage and air supply
The clay retains the water and supplies nutrients
Silt particles help to hold the sand and clay together

4. Soil Triangle

5. Soil Texture

6. Porosity, Permeability
Porosity: The amount of space between particles
Permeability: The ease at which gases and liquids pass through
Clay soils have lots of micropores
Results in lots of pore space, but low permeability
The water adheres the clay surface
Also locks dissolved minerals between pores making it hard for plants to access (high mineral content yet low fertility)
Sandy soils have fewer macropores
Less total space
Pores are too large for adhesion and therefore have a high permeability

7. pH Soil Acidification Soil Acidification and the Economy
Clay soils also tend to be more acidic
As more water is absorbed, the clay fills with hydrogen ions
Also reduces ability to store other positive ions and minerals are lost through leaching
The reduction in pH also makes toxic ions available to plants like iron and aluminum
Soil Acidification and the Economy
In Northern Europe acid rain has turned the soil acidic, making more aluminum and iron available, causing damage to forestry industry through needle death

8. Soil Sustainability Fertile Soil is a NON renewable resource? NPK
Formation takes a long time
Soil use often exceeds soil formation
NPK
Fertile soil contains enough nutrients for healthy growth
Nitrates, phosphates, and potassium are the major ones
There are many micro nutrients as well
Nutrients can be leached out of soil, or are removed when crops are harvested
Normally nutrients return to the soil via decomposition
Must be replaced for agriculture