1. Soil

2. Components of Soil
The four components of soil are minerals, organic matter, air, and water
The minerals come from rocks that have been broken down into tiny particles
Organic matter is called humus and comes from the decay and waste products of living things and provides nutrients for plants
Between the minerals and humus are small spaces called pores containing air and water

3. Components of Soil Soil supports many organisms other than plants
Fungi, insects, worms, and bacteria live in the soil and help decompose the organic matter

4. Soil Layers Soil is made up of a number of layers
The top layer is the litter, made of partially decomposed material. It reduces water loss and limits temperature changes
The second layer is the topsoil, made of minerals and humus. It is rich in nutrients, oxygen, and water, allowing plants to grow. Topsoil appears black because of the humus

5. Soil Layers
The third layer is the subsoil, made of more minerals and less organic matter than topsoil. It is lighter in colour due to lack of humus
The bottom layer is the bedrock, made of solid rock
Litter
Topsoil
Subsoil
Bedrock

6. Soil Nutrient Cycles
Soil health is important to ensure the plants will grow and ecosystems will be maintained
The amount and availability of nutrients is the number one factor in keeping soil healthy
Nitrogen, phosphorus, and potassium are the most important nutrients
These nutrients are cycled in ecosystems through producers, consumers, and decomposers

7. Soil Nutrient Cycles
When crops grow on farms, some of the nutrients are stored in the plant tissues and removed from the ecosystem
Nutrients have to be returned to the original soil, or it will gradually run out of nutrients

8. Fertilizers Fertilizer is any substance that helps plants grow
Using fertilizer is the most common method used to replace nutrients
Natural fertilizers such as manure can be mixed into the soil
Synthetic fertilizers go through chemical processes, but have the same nutrients
They can be sprayed or spread on fields and nutrients are immediately available
Synthetic fertilizers increased both food production and farm profits

9. Environmental Impact
Fertilizers can alter the organisms that are found in the soil
The soil may have less organic matter that naturally supplies nutrients and the soil will become dependent on fertilizers, which is not sustainable
During heavy rains or spring thaw, fertilizers can flow into aquatic ecosystems
Excess nutrients in water causes algal blooms that reduces oxygen, leading to death of fish and other organisms

10. Soil Pores
Soil needs pores to allow water and nutrients to pass through
Oxygen is provided to plants through pores
If soil is compacted too much, plants won’t grow well and water won’t drain properly