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Variations in Natural Nitrogen‐15 Abundance as an Aid in Tracing Fertilizer Nitrogen Transformations
Author(s) -
Karamanos R. E.,
Rennie D. A.
Publication year - 1980
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1980.03615995004400010013x
Subject(s) - fertilizer , nitrogen , abundance (ecology) , agronomy , isotopes of nitrogen , environmental science , soil horizon , isotope , chemistry , irrigation , soil water , soil science , biology , ecology , physics , quantum mechanics , organic chemistry
Rapeseed plant tissue and composite soil samples from field fertility plots were assayed for total N and inorganic N content, respectively, and corresponding 15 N abundance. Lower δ a 15 N values were obtained for subsurface horizons containing residual fertilizer‐N in both dryland (−2.0) and irrigated (ave. −3.5) plots compared to the surface horizons (3.4 and ave. 8.6). A systematic decline in the δ a 15 N values of the plant tissue was observed with irrigation application (20 and 30 cm) and application of N fertilizer (220 kg/ha). This was attributed in both instances to the increased contribution of fertilizer N to the plant. Calculation of the mass balance of the two isotopes in the fertilized dryland treatment indicated that no significant fractionation had occurred during N uptake by plants but the differences in the δ a 15 N values represented changes in soil N. While this study has clearly demonstrated the potential of utilizing variations in natural 15 N abundance to trace the fate of applied fertilizer N, it has also shown that it is of utmost importance to recognize the N transformations that have taken place in the soil‐plant system and the isotope effects that accompany them.