urea-treated plants (U2 and U1), on the other hand, the
lowering of d15N of each part due to urea addition was
evident at 20 DAT, but the value was not different among
plant parts at 20 and 40 DAT except for U1 plants at 20
DAT. However, intra-plant d15N variations became
different among the treatments at 60 DAT after additional
N application (Table 3), again reflecting the isotopic
composition of N source.