Spatiotemporal heterogeneity of soil nitrogen (N) strongly shapes root architecture, which governs crop N uptake and yield. This root-N interaction is particularly critical in water-limited dryland systems but remains poorly understood. We investigated the combined effects of N placement depth (5, 15, 25, and 35 cm) and rate (158, 191, 225 kg N ha 1 ) on spatiotemporal dynamics of soil N availability, root traits (root length density, surface area density, penetration depth, and root-shoot ratio), N uptake, N use efficiency, and grain yield of dryland spring maize on the Loess Plateau across two contrasting rainfall seasons. Relative to conventional N management (i.e., 225 kg N ha 1 at 5 cm soil depth), moderate N reduction with deeper placement (191 kg N ha 1 at 35 or 25 cm depth) significantly increased root length and surface area by 21.59 % and 17.78 %, respectively, promoting greater acquisition of subsoil resources. Correlation and path analyses indicated that N-induced improvements in root traits directly enhanced nitrogen use efficiency and stabilized maize yield, particularly under the drier growing season, where middle-deep roots (20-100 cm) were the primary yield contributors, whereas shallow-middle roots (0-60 cm) dominated in wetter years. We propose a rainfall-adaptive nitrogen management strategy, involving 35 cm placement with a 15 % nitrogen reduction in dry seasons and 25 cm depth in wet years. By synchronizing nitrogen application with environmental conditions, this approach enhances resource use efficiency, reduces nitrogen losses, and improves yield stability across diverse climate scenarios.