1. Basics of Soil What is soil?
Answer: Soil is loose, weathered material on the surface which plants can grow in.
Soil comes from weathering of solid bedrock.
What is soil made of?
Answer: Soil is a mixture of rock particles, minerals, decayed organic material, water, and air.
Fertility is a measure how well plants will be able to grow in certain soils.
Humus is dark colored organic (decayed previously living) material and is very fertile.
Sandy soils have low fertility.
Having an about equal number of different soil particle sizes (loam) is ideal for plant growth.
Clay holds lots of water and little air so plants may drown.
Sand holds lots of air, but water drains easily (think beach) so plants may dry out.

2. Soil profiles

3. Layers of Soil O - Organic Layer A – Agricultural Top Soil B – SuBsoil
Uppermost layer with lots of decomposing organic matter (leaf litter, insects, twigs); humus
A – Agricultural Top Soil
Mineral-rich organic matter (darker) with plant roots
B – SuBsoil
Transition level between A and C so has lots of clay and humus; low in organic material.
C – Parent Material (UnConsolidated)
Weathered rock and little/no organic matter
R – BedRock
Deepest and toughest layer; solid.

4. Layers of soil (Trends)
As you go deeper in the soil:
Organic material decreases
Fertility decreases
Weathering decreases
Becomes more dense
More gravel and boulders