Quantitative evidence of overestimated rhizodeposition using 15N leaf-labelling

The leaked 15N together with ordinary rhizodeposits (rhizodeposits released after the first day of labelling) led to an overestimation of N rhizodeposition by 70 ± 30% at the end of the six weeks lasting experiment using the isotope approach. The observed 15N distribution in roots and long-term 15N translocation from shoots to roots did not correspond to the expected distribution following classical pulse labelling. Thus, leaf-labelling with 15N-urea should not be considered a pure pulse-labelling method.