Abstract
Details are presented of a simple mathematical framework that allows 15N tracer experiments to be interpreted in terms of the main processes of the soil/plant nitrogen cycle. The calculations, all of which can be performed on a scientific calculator, yield the rates of gross mineralization and nitrification and the crop nitrogen uptake occurring as ammonium and nitrate. Two procedures are presented. One requires paired experiments with labelled ammonium and unlabelled nitrate as one treatment, and unlabelled ammonium and labelled nitrate as the other. The second procedure requires only the labelled ammonium, unlabelled nitrate treatment. Example calculations are presented using actual experimental data.
The interpretative procedure uses the fact that the rate of isotopic dilution in an ammonium pool labelled with 15N is a function of the rate at which unlabelled ammonium is introduced into the pool via mineralization. Similarly, the rate of isotope dilution in an 15N labelled nitrate pool is a function of the rate at which unlabelled nitrate is introduced into the pool via nitrification.
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Barraclough, D. The use of mean pool abundances to interpret 15N tracer experiments. Plant Soil 131, 89–96 (1991). https://doi.org/10.1007/BF00010423
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DOI: https://doi.org/10.1007/BF00010423