Microscale-scale measurement of potential nitrification rates of soil aggregates

To improve our knowledge about the effect of soil structure on potential nitrification (PN) rates in different soil aggregate fractions, we adapted and validated the standard method based on International Organization of Standardization (ISO) 15685 to small sample volumes. This assay was used to determine the distribution of PN in soil aggregates obtained from three different sites (natural grassland, agricultural land and forest). Overall, the external surface layers of the aggregates showed higher PN rates than the interior fractions of the aggregates. These differences were more clear in clayey than in sandy soils.