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The Use of the Nitrogen Isotope N 15 in Determining Nitrogen Recovery from Plant Materials Decomposing in Soil 1
Author(s) -
Norman A. G.,
Werkman C. H.
Publication year - 1943
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1943.00021962003500120004x
Subject(s) - citation , agricultural experiment station , isotopes of nitrogen , nitrogen , soil water , library science , agriculture , mathematics , environmental science , chemistry , computer science , archaeology , history , soil science , organic chemistry
THE USE OF THE NITROGEN ISOTOPE N IN DETERMINING NITROGEN RECOVERY FROM PLANT MATERIALS DECOMPOSING IN SOIL MANY practical agronomic problems center round the availability and recovery of the nitrogen of crop residues. The nitrogen transformations that occur when plant materials are incorporated in the soil are complex, though the general principles underlying them have probably been established. Studies in this field, however, will acquire a greater degree of precision and certainty when the nitrogen isotope of mass 15 is used as a tracer. This isotope can now be obtained in the form of ammonium nitrate, the ammonium ion of which is enriched very substantially above the normal figure of 0.38 atom %. Enriched nitrate can, however, be prepared by distilling off the ammonia and submitting it to biological oxidation in a percolating filter in which an active nitrifying population has been developed. If organic sources of nitrogen containing the isotope are desired they can be obtained by supplying an appropriate plant with an enriched ammonium or nitrate salt. With these three forms available it will be possible to examine in detail the nitrogen changes involved in the decomposition of plant materials. The chemical properties of the isotope are, of course, identical with those of the normal form, so that it appears in the tissues of plants and microorganisms in the same proportion as in the source of nitrogen supplied. Accurate figures for the quantity of nitrogen immobolized by low-nitrogen residues will be obtainable by adding an enriched inorganic source and following the distribution of the isotope in the organic form at intervals. Likewise, the rate and amount of