Not so simple.

"Oilseed rape is known for its high capacity for N, water uptake, and potential to develop roots in soil layers below 2 m (Dresbøll et al., 2016; Kirkegaard et al., 2021). In this study, we used oilseed rape as the model crop and examined how N and water supply affect the root growth, utilization of N and water from deep soil layers, and N and water uptake dynamics in the subsoil. It was hypothesized that (I) N and water deficiency in topsoil stimulate root growth in deeper soil layers; (II) lower N availability in the upper soil layer reduces total water uptake, but enhances N uptake from the subsoil; (III) lower water availability in the upper soil layer reduces the N uptake from the whole soil profile, but increases water uptake from the subsoil." A citation from: Chen, Guanying, et al. "Dynamics of Deep Water and N Uptake of Oilseed Rape (Brassica napus L.) Under Varied N and Water Supply." Frontiers in Plant Science 13 (2022): 866288.