Fig. 2: Vertical patterns of soil inorganic nitrogen in global croplands.
From: Preventing subsoil enhanced nitrification to safeguard agroecosystem sustainability
a, b Vertical profiles of soil ammonia nitrogen (NH4+-N, nitrification substrate) and nitrate nitrogen (NO3--N, nitrification product) in global croplands, respectively. The coloured dot line represents the mean values (±95% confidence interval) at each soil depth, with the adjacent numbers indicating the sample sizes. The gray dots represent the distribution of the sample values at varying depths. The site locations of soil NH4+-N and NO3--N in global croplands are presented in the world map at the lower right corner. Soil NH4+-N and NO3--N of varying depths are compiled from literature and are detailed in Supplementary Tables 6 and 7. ENL denotes the enhanced nitrification layer.
