Pregitzer, Kurt S., authorPaul, Eldor A., authorHorwath, William R., authorSoil Science Society of America, publisher2007-01-032007-01-031992-01Horwath, William R., Eldor A. Paul and Kurt S. Pregitzer, Injection of Nitrogen-15 into Trees to Study Nitrogen Cycling in Soil. Soil Science Society of America Journal 56, no. 1 (January-February 1992): 316-319. https://dx.doi.org/10.2136/sssaj1992.03615995005600010051x.http://hdl.handle.net/10217/85525Most 15N dilution techniques disturb either the soil or N-pool size. The objective of this study was to develop a method of labeling the roots of Populus trees with 15N without physically disturbing the soil. Such a method would enable the direct measurement of the flux of 15N from dead roots into the soil organic matter. Leaf and root biomass were labeled by injection of 15N directly into the vessel elements of hybrid Populus trees during their second growing season. The 15N was uniformly distributed throughout the canopy and root system. The rate and amount of 15N turnover from plant tissue can be determined by pool transfer or through differences in plant 15N concentrations. The 15N was detected in the dead-root pool 8 wk after injection, indicating root turnover. Results demonstrate the ability to measure the contribution of fine-root litter to N-cycling processes without disturbing the soil environment.born digitalarticleseng©1992 Soil Science Society of America.Copyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright.plant residueN transformationN processes15NfertilizerTexthttps://dx.doi.org/10.2136/sssaj1992.03615995005600010051x