Rainfall limit of the N cycle on Earth

[1] In most climates on Earth, biological processes control soil N. In the Atacama Desert of Chile, aridity severely limits biology, and soils accumulate atmospheric NO3 . We examined this apparent transformation of the soil N cycle using a series of ancient Atacama Desert soils (>2 My) that vary in rainfall (21 to <2 mm yr1). With decreasing rainfall, soil organic C decreases to 0.3 kg C m2 and biological activity becomes minimal, while soil NO3 and organic N increase to 4 kg N m2 and 1.4 kg N m2, respectively. Atmospheric NO3 (D17O = 23.0%) increases from 39 % to 80 % of total soi