Nitrogen turnover in soil after application of animal manure and slurry as studied by the stable isotope 15N:: a review

In the last decades many aspects of nitrogen turnover have been studied by N-15 methods. In this article contemporary N-15 tracer as well as natural N-15 abundance methods for the study of animal manure turnover are briefly reviewed. The nitrogen dynamics after application of farmyard manure and slurry are elucidated. Here, emphasis wa put on results from N-15 stable isotope work in the fields of nitrogen immobilization, nitrogenous trace gas emissions, turnover of organic nitrogen fractions, and finally plant uptake. Added nitrogen interactions, which must be considered when interpreting N-15 studies, are discussed. Finally promising research fields for the use of stable isotopes are outlined.