Study sheet:
Nitrogen cycle
The movement of nitrogen through the ecosystem, the soil and the atmosphere.
1. Nitrogen atoms are released into the atmosphere in the process of decay, in plant and animal
tissues
2. These nitrogen atoms from nitrogen gas in the atmosphere, which is converted into nitrates
through nitrogen fixation. These nitrates then dissolve in our rain and enter our soil.
3. Through the process of osmosis the plants absorb the water with the dissolved nitrates.
4. When the plants are consumed, the nitrates pass from the producer to the consumer
5. When the animal dies, the nitrates are released back into the atmosphere.
6. And the process repeats
The Importance of Nitrogen for Living Things
All life depends on the cycling of nitrogen, our cells use these nitrogen atoms to produce proteins
which are then made into DNA. Nitrogen is also a critical limiting nutrient in many ecosystems
including the forests, wetlands, and our oceans. Due to our agricultural sector, human activities
account for over 1/3 of dinitrogen monoxide (N2O) emissions.
Five major effects of Nitrogen oxide and nitrogen nitrate emissions:
1. The emissions decrease atmospheric visibility due to fine particles called ammonium aerosols
(PM)
2. It increases our ozone concentration
3. Cancer and respiratory diseases are just some of the negative effects that Ozone and Pm have
on human health
4. It increases global climate change.
5. Due to the ozone decomposition there is a decrease in our agriculture productivity.
Nitrogen fixation

Nitrogen Fixation is two processes in which atmospheric or dissolved nitrogen is converted into
nitrate Ions

There are two to convert atmospheric nitrogen into nitrates:

First method: Lightning
The energy from the lightning bolt causes the nitrogen gas to react with the oxygen in the air which
results in the production of Nitrates. After production, the Nitrates are then dissolved in rain or surface
water, like our lakes or ponds. They enter the soil and move into plants through their routes in a
process of osmosis. The plant cells use these nitrates to make DNA, and amino acids which the plants
then use to make proteins. When the plant is consumed by another animal those proteins travel from
the plant to the animal. The animal then breaks down these plant proteins into their own amino acids
for their own use.

Second method: Bacteria
Some types of bacteria are also able to convert small amounts of nitrogen into nitrates. They provide
the ecosystem with the vast majority of nitrates which can be found in the soil.Nodules: Small lumps of
nitrogen-fixing bacteria that can be found on the roots of legumes such as clover, peas, soybeans and
alfalfa. These types of bacteria provide the plants with a supply of usable nitrogen, the plants provide
the Nodules the sugar or energy they need to make the nitrates.
Decomposition
Sometimes there is more nitrates produced then needed, so the excess nitrates go into the soil for other
plants to use.

When organisms produce waste and eventually die, Decomposers chemicals containing nitrogen
in the body into simpler chemicals like ammonia.

There bacteria do require oxygen to function

The ammonia is then converted into nitrites by other bacteria and the nitrites are then
converted into nitrates.

The nitrates continue through the cycle, plants absorb these nitrates through the roots and then
use the chemicals to make cell proteins and finally DNA.
Purpose of Crop Rotations
Advantages of Crop Rotation:
1. Maintains soil fertility
2. Reduces Soil erosion
3. Controls pests like insects and mites. Crop rotation is the most effective way to control insect
pests.
4. Reduces reliance on synthetic chemicals
5. Prevents diseases
6. Help control weeds
Crop insects and pests are usually host specific. If you don’t rotate your crop, the pests will have
food always available. If you rotate your crops with a different crop family, the pests will die from
lack of food. Iroquois traditionally planted three plants together; the bean, corn, and squash; and
these plants became known as the “three sisters”. These crops helped each other thrive while also
protecting the soil. Corn provided scaffolding for the other plants, while the beans added nutrients
to the soil. The squash prevented water evaporation and erosion, while also helping control the
growth of weeds. This is where we got the idea of crop rotation
Denitrification is carried out by bacteria that break down nitrates into nitrites, and nitrites into nitrogen
gas. These bacteria do not require oxygen, and seem to thrive in soil that is acidic or water-logged.
For example: Bogs can only support a few plants; these plants obtain their nitrogen from digesting
trapped insects. Denitrifying bacteria are a problem for gardeners. This bacteria often grows best where
there is no oxygen, and exposing the bacteria to oxygen slows the breakdown of nitrates into nitrogen
gas As a result gardeners have to aerate their land before planting so the nitrates can be drawn in by
grass roots and be used to make proteins.