Isotope effects in relation to the interpretation of $sup 15$N/$sup 14$N ratios in tracer studies

Conference · Wed Jan 01 04:00:00 EST 1975

OSTI ID:4148467

Edwards, A P

Data from aerobic incubation studies involving application of $sup 15$N- depleted, $sup 15$N-enriched and natural-abundance aqua-ammonia fertilizer to a Webster soil have been used to calculate the change in isotope concentrations produced by isotope effects acting on the portion of the fertilizer ammonium converted to nitrate. The nitrate-N from the fertilizer sources contained significantly more $sup 15$N than the ammonium-N applied, which is exactly opposite to the result to be expected in a pure system where ammonium is undergoing partial nitrification only. A model to explain these results, and to illustrate the probable sequence of changes in cropped soils, is presented. The significance of isotope effects with respect to the interpretation of $sup 15$N/ $sup 14$N ratios actually measured during tracer investigations is greatest where an attempt is made to use the natural-abundance approach to quantitative separation of sources. The possibility of using small changes in isotope concentration to elucidate soil reaction mechanisms is shown to be extremely unlikely because partial conversions of unknown magnitude are the rule rather than the exception in soils. (auth)

• Research Organization: Univ. of Nebraska, Lincoln
• NSA Number: NSA-33-007654
• OSTI ID: 4148467
• Country of Publication: IAEA
• Language: English

Related Subjects

*NITROGEN 14
*NITROGEN 15
*SOILS-- ISOTOPE RATIO
551200*
FERTILIZERS
N48810* --Life Sciences--New Tracer Techniques--Animal Husbandry
TRACER TECHNIQUES