Variations in the Natural Abundance of 15N of Wheat Plants in Relation to Fertilizer Nitrogen Applications

• Published in: Soil Science Society of America journal Vol. 39; no. 5; pp. 896 - 901
• Main Authors: Shearer, Georgia, Legg, J. O.
• Format: Journal Article
• Language: English
• Published: Soil Science Society of America 01-09-1975
• ISSN: 0361-5995; 1435-0661
• DOI: 10.2136/sssaj1975.03615995003900050030x

Measurements were made by two laboratories of the δ15N (per mill 15N excess) of winter wheat plants (Triticum aestivum L.) grown at five locations in Pennsylvania on experimental plots. The plots were fertilized with N at various rates. The results from both laboratories showed a consistent decline in δ15N with increasing rates of N application. Such a decrease in δ15N is consistent with increasing contributions of fertilizer N to the plants as the rate of application increased, given that fertilizer N has a lower 15N content than the soil N. The coefficients of regression of δ15N of wheat on N application rate were always negative and usually significantly different from zero. The regression coefficients computed from the results of the two laboratories were not significantly different from each other in 12 of 16 experiments. There was, however, a systematic, unexplained difference in the results from the two laboratories. A regression of one set of data on the other resulted in a regression coefficient significantly different from one, the theoretically expected value.