N₂ (atm ≈78%) fixed into NH₄⁺/NO₃⁻ by bacteria or Haber–Bosch; nitrified, assimilated into biomass, denitrified back to N₂/N₂O. Haber–Bosch now contributes ~100 Tg N/y, doubling the pre-industrial flux.
N₂ (atm ≈78%) fixed into NH₄⁺/NO₃⁻ by bacteria or Haber–Bosch; nitrified, assimilated into biomass, denitrified back to N₂/N₂O. Haber–Bosch now contributes ~100 Tg N/y, doubling the pre-industrial flux.