bio

Nitrogen fixation

The conversion of inert atmospheric nitrogen gas (N₂) into a chemical form life can use, performed by certain bacteria — many living symbiotically in the roots of pioneer plants. It is the decisive bottleneck on fresh volcanic ground: new tephra can be rich in phosphorus, potassium and calcium but carries almost no biologically available nitrogen, because the heat of the eruption drove it off. Nitrogen is the element life needs in bulk and cannot easily improvise. Without a nitrogen- fixer to prime the pump, most plants simply starve on rock that looks, chemically, half-fertile.