Quantification of changes in decomposable N fractions caused by atmospheric N inputs - A ¹⁵N balance study

Abstract

In a field experiment we analysed the ¹⁵N/¹⁴N ratios in hot- and coldwater soil extracts, salt extracts (KCl), leachates as well as in the soil vegetation for quantifying the impacts of atmospheric N inputs on soil N dynamics. We simulated moderate and chronically high N inputs and determined the forms, contents, and atom% from December 2001 to November 2002 in a German Scots pine forest stand. A maximum of 90% of the total ¹⁵N in the soil was extractable by the KCl, hot- and coldwater soil extraction methods in strongly dependence of the soil horizon. The highest ¹⁵N recovery was calculated for the organic layer and the Ah horizon. After one year, only 2% of the added ¹⁵N was leached below the C2 horizon (−100 cm), whereas up to 11% were found in the soil vegetation. About 70% of the added ¹⁵N was lost by nitrification and denitrification processes during the experiment.

Keywords:

• ¹⁵N
• diffusion method
• total nitrogen
• water extractable nitrogen
• KCl extractable nitrogen
• mass spectrometry

Acknowledgements

The author gratefully acknowledges the German Research Foundation for a research fellowship within the graduate college 339 to carry out this study at the Institute of Soil Science, Dresden University of Technology.