Aims: Deep-rooted crops have been widely used in agricultural systems to access deep resources such as water and nitrogen (N). However, the potential of deep roots to take water and N at various depths have not been well studied. Here we used chicory (Cichorium intybus L.) to study the potential and dynamics of water and nitrogen uptake in deep soil layers (below 1 m). Methods: Chicory plants grown in outdoor rhizotrons were labelled by injecting a ²H₂O and Ca(¹⁵NO₃)₂ mixture into the soil column at 1.1, 2.3 and 3.5 m depth. Five, ten and twenty days after injection, ²H and ¹⁵N were traced in transpiration water and leaves. Results: We found enriched ²H and ¹⁵N in water and plant samples, and both water and N uptake were observed down to 3.5 m. The ²H enrichment after injection at 1.1 m depth was 1552‰, almost 10 times higher than after injection at 2.3 m depth, which was 156‰. In contrast, injection at 1.1 and 2.3 m depth resulted in similar ¹⁵N enrichment of leaf samples. Conclusion: Deep water uptake was found to be more sensitive to increased depth and reduced root intensity than N uptake, and labelled N was used more rapidly than labelled water. We propose several possible explanations for the discrepancies between deep water and N uptake, and further discuss the challenges of using isotopes and models in deep root studies.