Fig. 1: Vertical patterns of soil total nitrogen (TN) in global croplands and non-croplands.
From: Preventing subsoil enhanced nitrification to safeguard agroecosystem sustainability
a Site distribution of soil TN in both global croplands and non-croplands. Global soil TN data are obtained from the existing database of the World Soil Information Service (WoSIS) and extensively compiled from the site-level investigations of croplands in the literature (Supplementary Tables 6 and 7). Sites from the WoSIS are classified into cropland and non-cropland types based on the global distribution of land uses at different periods (see Methods). b, c The exponential decline and peak patterns of soil TN in global non-croplands and croplands, respectively. The data are shown with a mean ± 95% confidence interval. d, e Soil TN change at 0.6 m depth compared to the mean of the adjacent five soil layers (the main subsoil depths within 1 m where nitrification occurs, based on refs. 48,49,50,51) across time, as well as its relationship with global mean nitrogen input, respectively.
