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. Ä15N values for fertilizer nitrogen ranged from -4.1 to 1.9 and for nitrate nitrogen in water from 4.4 to 6.1. Ä15N 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 Ä15N of nitrate released by mineralization between replicates and within each sampling site was small. The Ä15N for nitrate released under bare fallow was 5.5. The use of these variations in 15N abundance is discussed. The Ä15N values for nitrate from soil intervals to 6M increased with depth. This result is discussed in terms of fractionation in a nitrate adsorbing soil.