12: The Global Cycles of Nitrogen, Phosphorus and Potassium Last updated Save as PDF Page ID 19353 12.1: Introduction 12.2: The global nitrogen cycle 12.2.1: Chemistry of the nitrogen cycle 12.3: Temporal variations in the global nitrogen cycle 12.4: Nitrous Oxide (N2O) 12.4.1: Terrestrial 12.4.2: Marine 12.4.3: Human Sources 12.5: The global phosphorus cycle 12.6: Potassium- An overlooked limiting element? 12.7: Linking global biogeochemical cycles 12.8: Summary