1. The Nitrogen Cycle Chapter 2

2. Nitrogen The circular flow of nitrogen to free gas in the atmosphere (it is 78% of our atmosphere), to nitrogen compounds (such as nitrates) in the soil, back to atmospheric nitrogen. In it’s elemental form (not a compound), it is a colorless, odorless gas. It must be combined with oxygen or other elements before it becomes available as a nutrient for living organisms. Plants and animals use nitrogen compounds to form DNA and proteins and vitamins.

3. Nitrogen Cycle Nitrogen fixation-a process by which nitrogen gas from the atmosphere is converted to nitrates. This can happen in several different ways: – Nitrogen-fixing bacteria can convert gas to nitrates. Some of these bacteria live in the soil, and others live in nodules on the roots of legumes (like beans). – Several industrial processes convert the gas to nitrates. Ammonia gas (a by-product of steel making) can be converted to nitrates. These nitrates are used as fertilizers.

4. Nitrogen Cycle continued… – Nitrogen fixation also occurs naturally when lightning strikes. – Nitrates are also released when plants and animals decay, or from animal wastes.

5. Nitrogen Cycle continued… Denitrification is the process where nitrates are broken down and the nitrogen is released back into the atmosphere. – Happens by some bacteria – Also happens when nitrates are carried off by surface water, which constantly exchanges nitrogen with the atmosphere.

6. The Nitrogen Cycle, with pictures and arrows… Please look at Figure 2-10, on page 27.