We are studying the uptake and internal recycling of nitrogen in perennial crops using 15N labeled N sources.
As part of the NEWBio project, an experiment was set up at Rock Springs (near State College, PA) with the shrub willow cultivar 'Preble'. Nitrogen with 5% 15N enrichment was added to root enclosures to label individual shrub willow plants. This allows tracking nitrogen uptake, storage, and its re-use in successive growing seasons. The plants in the picture have less than one year of aboveground growth.