Abstract
Natural 15N abundances (d15N) in plant and soil can be used as a powerful marker to reveal the history of N fertilization. To
investigate whether N fertilizer source and timing of fertilization leave specific d15N signals in plant tissue and soil inorganic N, Chinese
cabbage (Brassica campestris L. cv. Maeryok), one of the most popular vegetables in Asia, was grown in pots for 60 days with a single or
split N applications of organic (composted manure; d15N ¼ +16.4%) or inorganic N (urea; d15N ¼ 0.7%). Seven N treatments were
studied: (1) a single basal fertilization with compost or (2) urea; (3) a basal urea application followed by an additional (at 40 days after
transplant, same below) compost or (4) urea application; (5) a basal compost application followed by an additional compost or (6) urea
application; and (7) no N fertilization. Regardless of the time of N application, d15N of cabbage treated with compost was higher
(4+9.0%) than that (o +1.0%) treated with urea, reflecting the effect of isotopically different N sources. In split N fertilization, only
the addition of isotopically different N sources in the middle of the growth period significantly affected the d15N of the whole plant.
Specific d15N signals of basal N inputs were detected in outer cabbage parts formed in the early growth stage, while those of additional N
inputs were detected in inner cabbage parts formed in the latter growth stage. We conclude that measurements of temporal variations in
d15N of plant parts formed in different growth stages could reveal the history of N fertilization.
r 2006 Elsevier Ltd. All rights reserved.