Heterogeneity of nitrification potentials within a paddock of a sheep farming system

Nitrification and denitrification are important processes of the nitrogen (N) cycle in soils because of their relations to N availability for plants and to environmental risks. However, paddock scale heterogeneity of these processes is not well understood in pasture ecosystems. Thus, we focused on the variability of nitrification and denitrification potentials within one pasture paddock. Twelve soil samples were taken from various places within a 2.3 ha paddock in September and were analyzed for nitrification and denitrification potentials, inorganic‐N, total carbon (C) and N, C/N ratio, soil pH and moisture contents. The variability of the denitrification potentials was smaller than that of the nitrification potentials. We found that inorganic‐N, total C and N, and soil pH were positively correlated to the nitrification potential. We also identified a “hot‐area” with 3.3‐fold higher nitrification potentials than other areas. A better understanding of this paddock scale nitrification variability may help to decrease environmental risks, such as nitrate leaching and/or nitrous oxide emissions, and to improve N use efficiencies.