While organic compost contains nitrogen, compost alone often does not provide an adequate supply for these plants. These plants collaborate with soil bacteria to absorb nitrogen from the air and deposit it in tiny root nodules—a process called nitrogen fixation. Some plants need more nitrogen than others, such as roses, corn, and lettuce.
- Review the basic functions of soil.
- Plant favas, alfalfa, or peasto fix nitrogen.
- Add soil amendments to fix nitrogen.
- Examples of nitrogen-fixing organic material, such as fava beans, soil amendments, or fish emulsion.
- Fava beans with nitrogen nodes.
- Review all the things that living things need to survive that students have learned in past lessons (light, air, water, sun, nutrients, and animal habitats).
- How do we get our nutrients? (Healthy foods)
- How do plants get their nutrients? (They make their own food through a process we will learn more about, called photosynthesis. They also get nutrients, like nitrogen, through other plants, the air, and animals.)
- Soil performs four major functions:
- Habitat for organisms
- Recycles raw materials
- Provides the foundation for engineering projects such as buildings, roads, and bridges
- Supports plantgrowth
- Show examples of nitrogen-fixing organic, such as manure amendments. Show fava beans with nodes to describe how they fix nitrogen into the soil.
- Share facts about nitrogen:
- Nitrogen is the most common gas found in the earth’s atmosphere
- It is necessary for plant growth.
- Gardens get nitrogen from the atmosphere, animal waste, and decaying and dead organisms.
- Compost requires aerobic conditions for air or oxygen in order for decomposing bacteria to keep nitrogen in the soil.
- This cycle reduces the amount of food waste in our landfill and produces rich soil.
Fixing Nitrogen In the Garden
- Divide students into small groups to work in the garden onprojects that provide nitrogenfor plants:
- Plant fava beans
- Add nitrogen fixing amendments to the soil
- Turn the soil to aerate it
- How can we fix nitrogen into our soil to help plants grow? What does fixing nitrogen mean?
- Nitrogen: is a nutrient that is commonly in limited supply. Nitrogen deficiency in plants can occur when organic matter with high carbon content, such as sawdust, is added to soil.
- Aerate: to expose to the action or effect of airor to cause air to circulate through.
- Aerobic Conditions: Requiring air or oxygen for life or survival. Some bacteriaare obligate aerobesthat require oxygenfor respiration.
- Anaerobic Conditions: Not requiring air or free oxygen.
Disciplinary Core Ideas
Natural Resources: Living things need water, air, and resources from the land, and they live in places that have the things they need. Humans use natural resources for everything they do
This lesson is part of the Berkeley Unified School District's Gardening and Cooking Program curriculum.