The natural abundance of 15N in the soil water system of a small catchment area

Abstract

The 15N abundance in components from a 100 ha catchment was determined. �15N values for fertilizer nitrogen ranged from -4.1 to 1.9 and for nitrate nitrogen in water from 4.4 to 6.1. �15N values for total nitrogen from three sites ranged from 2.9 to 6.7 and for nitrate released during laboratory incubations from -0.2 to 4.2. The variability in �15N of nitrate released by mineralization between replicates and within each sampling site was small. The �15N for nitrate released under bare fallow was 5.5. The use of these variations in 15N abundance is discussed. The �15N values for nitrate from soil intervals to 6M increased with depth. This result is discussed in terms of fractionation in a nitrate adsorbing soil.