1. Nitrogen gas in air cannot be absorbed by plants
2. Nitrogen fixing converts N2 into nitrogen compounds
3. Deamination releases ammonia from animal urine
4. Decomposition releases ammonium ions
5. Nitrification converts ammonium to nitrites then nitrates
6. Plants absorb nitrates
7. Nitrogen used to make proteins and DNA/RNA
8. Denitrification converts nitrates back to nitrogen gas