Continental drivers of ammonium and nitrate in Australian soil under different land uses
Soil N is an essential element for plant growth, but its mineral forms are subject to loss to the environment by leaching and gaseous emissions. Despite its importance for the soil-plant system, factors controlling soil mineral N concentrations over large spatial scales are not well understood. We used NH4+ and NO3− concentrations (0–30 cm depth) from 469 sites across Australia, and determined soil controls on their regional variation. Soil mineral N varied regionally but depended on the different land uses. In the agricultural region of Australia, NH4+ tended to be depleted (4.9 ± 4.8 vs. 5.6 ± 9.0 mg N kg−1) and NO3− was significantly enriched (6.0 ± 9.2 vs. 3.8 ± 9.9 mg N kg−1), compared to the non-agricultural ecological region.