The Montessori Elementary child is presented with a number of lessons about plants. We have previously discussed the first 2 lessons of plants: 1. The Four Greek Elements and 2. What Nutrition Plants Need. These serve as an introduction to the idea of chemistry to the Elementary child. We’ve discussed the historical practice of leaving ground fallow and the modern practices of fertilization (with the example of cotton in the post Civil War south as the prime example). The third of these lessons is a discussion of Nitrogen and the Nitrogen Cycle. There are diagrams of each of the lessons that were created after Dr. Montessori did by a number of her followers. These diagrams lack the elegance for which Montessori works are known. Perhaps the most unsettling of the diagrams is the Nitrogen Cycle’s. So, Mrs. W and I worked out a hands-on work. We are open for suggestions.
- Chart 2 of “Plant nutrients”.
- Jar of air.
- Soybeans, peanuts or other legumes
- Chart 3 – nitrogen cycle in felt parts.
- 4 boxes with the parts.
- “Free Nitrogen”
- 10 tickets labled “N”
- 10 tickets labeled O
- 10 tickets labeled H
- “Nitrification box 1 – atmosphere”
- Cloud in grey felt
- Lightening with two branches
- “Nitrification box 2 – terrestrial”
- legume stalk and roots
- legume leaves
- nitrogen fixing bacteria
- poop x 2
- green leaves
- brown leaves
- bones for deer
- denitrification bacteria
- fungi – mycelia and mushroom
- “Free Nitrogen”
- Jar with soil.
Nitrogen Cycle Presentation:
Lay out the underlayment and place underground water table, tree, sun and clouds in their places. Open “Free Nitrogen” box.
Plants, like all organisms, require a certain number of chemical elements for growth.
The story of one of these, nitrogen, is an interesting one. Nitrogen is especially important because proteins are rich in it, and they carry out a lot of the work in the cells.
Take a deep breath. Slowly breath it out. Hold the glass of air up.
Even though 78% of the air we breathe is nitrogen, plants and animals can’t use the free nitrogen.
We breathe it back out.
Show Chart 2. Invite the children to recall the lesson and name the elements.
And out of the 12 or so elements that a plant must obtain from the soil, only nitrogen can’t be obtained directly. It must first be fixed – that is, combined with other elements usually hydrogen or oxygen. This happens in a two main ways. When nitrogen is fixed, it is called “Nitrification.”
Lay out the rest of the Free Nitrogen cards in the soil.
Open “Nitrification box 1 – atmosphere” box.
The first way nitrogen is “fixed” is in the atmosphere. The catch is that nitrogen will only bond with its favorite elements when there is high temperature and pressure. Where in the atmosphere will you have really high temperatures and lots of pressure?
In lightening bolts!
Lay out rain. Move an H2O into the stream of rain.
When the lightening bolts strike the nitrogen bonds with oxygen making Nitric oxide.
Move the second and third H2Os near the second branch of the lightening bolt and bring over a N, split it apart and allow the H2s out into the atmosphere. Join the NO2 together.
When the NO2’s fuse this is called nitrogen dioxide. The Nitric oxide falls to the ground with the rain. However, not all of the nitrogen dioxide falls directly to the ground. It bumps into some of the H2O’s. It then fuses and forms nitric acid.
Move the NO2s with waters and arrange them into nitric acid. Make sure all the nitric oxide, nitrogen dioxide, and nitric acid move into the soil.
These three types of fixed nitrogen that are made in the atmosphere are may be used by plants. This is three ways Nitrification takes place in the atmosphere.
Open “Nitrification box 2 – terrestrial” box.
In temperate soils, another types of fixation takes place in the roots of some plants.
Ask the children to name some legumes. Share the soybeans or peanuts. While the children chew, lay out the legume plant.
As these plants grow, their root hairs send out certain chemicals that attract root bacterias. When the bacteria touches the root hairs two things might happen. 1. if it is not the right type of bacteria the root protects itself for it. But, if it is the correct type of bacteria, it is held there,
Lay out the bacteria in the soil and move them to the roots of the legume.
and a kind of tube grows from each bacteria into the cells of the tiny root hairs. These bacteria enter into the cells and reproduce causing a swelling called a “nodule” on the root.
This is not an invasion that will hurt the plant. The bacteria and the plant are working together. Do you know the word that is made from the Greek word sym meaning together and the word bios meaning life?
The plant provides energy in the form of ATP and the bacteria bring an enzyme that takes the fixed nitrogen and combines it with hydrogen and that makes ammonia!
The ammonia is quickly converted into NO2 and NO3. Plants use these as fuel for growth. It is incorporated into many amino acids when are used to make proteins.
Make the NO2 and NO3.
The Oxygen from the water is not wasted but used as part of the process and then released. Nitrogen is stored in the leaves, fruit, and roots of the legumes and remember that the fixed nitrogen that was made by the lightening can be used by other plants. This is quite a bit of nitrogen hanging out in plants. But man needs nitrogen, too. How do we get nitrogen to help us grow?
Say a person, or a horse, or a deer comes along and sees some tasty soybeans or pulls up a peanut plant and finds tasty peanuts, what do they do? Ahhhhh.
Lay down the deer with him “eating” the legume.
Yes they eat it. Now the fixed nitrogens are inside the deer. I wonder how they might come out?
One way is for the animal to excrete waste. The animal might be a tiny earthworm or a giant whale. It still extracts what it can from its food; it can’t take all of the nutrients and some pass into the feces to be excreted from the body.
Open the “Denitrification” box.
We now begin the process of “Denitrification” – of breaking apart the fixed nitrogen into single nitrogen atoms to be used again.
Can you think of another way that the nitrogen trapped in a living thing can be returned to its denitrified state?
What about the plants? How does the trapped nitrogen leave the plants?
They will get it and will say that the trees and plants die.
Yes they do die, but some trees live a very long time. How about their leaves? On most trees, they live only one year and then fall off.
Put the green leaves falling and the brown leaves on the ground near the deer.
Bring out the mycelia and the mushroom, bring out the bacteria, move the earthworms over.
Take the nitrogen and oxygen in the deer and break it apart and return it to the atmosphere.
Take the nitric acid in the tree and break it apart and return it to the air. Put water back into the clouds and generally reset the cycle.
This important job of denitrification takes death and turns it back into what brings life and growth. The cycle may begin again.
Touch the clouds and walk through the cycle again using the major terms.
Now that you have had this lesson you may do this work. You must be very careful with so many ways and times that nitrogen fixes, you must be observant and thoughtful to cause the correct nitrification and denitrification at the correct time in the cycle.
- Volcanoes, power plants, and cars also can fix Nitrogen.
- A byproduct of denitrification is N2O or nitrous oxide, “laughing gas” and is considered a greenhouse gas.
- The oceans have their own nitrogen cycle which involves blue-green algae and other bacterias without having a symbiotic relationship with plants.
- Fertilizers and the Haber Process is its own topic and worth research by an upper el student.