Variations in the Natural Abundance of 15N of Wheat Plants in Relation to Fertilizer Nitrogen Applications
1975
Shearer, Georgia | Legg, J. O.
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.
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