Which process does not exist in nitrogen cycle ?
1
O2 + N2 \(\xrightarrow {h\nu}\) nitric oxide
2
oxide of nitrogen \(\xrightarrow {H_2O}\) nitric acid
3
nitrates \(\rm \xrightarrow {Rhizobium}\) nitrogen
4
ammonia \(\rm \xrightarrow{bacteria}\) nitrogen