Soil
Soil is…
• A combination of weathered rock (sediments), humus (decaying organic matter such as dead plants and animals), air and water
In order for soil to form…
• Bedrock weathers into sediments
And
• Organic matter (dead plants and animals) decay to form humus.
Sediments and humus mix
Quiz your partner
• What does soil contain? • How does it form?
The Nitrogen Cycle
• Healthy soil contains Nitrogen for plants to absorb into their roots.
Animals eat plants to get Nitrogen
• Nitrogen makes proteins. So when you eat protein you are eating Nitrogen.
Protein
• Every structure in a living organism is made of protein…your DNA, cells, eyes, everything!
• So, organisms need protein and the Nitrogen to live.
Quiz your partner
• Why is Nitrogen important? • How do plants get it? • How do animals get it?
Nitrogen is now in plants and animals
• When the plant or animal dies, this Nitrogen returns to the soil through decomposition.
• Manure
The air is mostly Nitrogen
• Nitrogen in air gets into the soil through Nitrogen Fixing.
• Nitrogen Fixing bacteria in roots can change Nitrogen in the air into Nitrogen in the soil.
• Lightening can also fix Nitrogen.
Quiz your partner
• How does get Nitrogen get into the soil (there are four ways)?
Nitrogen returns from soil to the air
• Bacteria can change the Nitrogen in the soil back into Nitrogen in the air.
It is a cycle-draw and put your notes into the cycle
Quiz your partner
• Describe the entire Nitrogen cycle from the Nitrogen in the air to the soil to the plants, to the animal, back to soil and back to air.