Rain-fed agroecosystems require integrated strategies to synchronize water and nitrogen use for sustainable production. To investigate the mechanisms by which ridge-furrow planting (RP), coupled with optimal N rate (90, 135, 180 kg N ha-1), enhances soil water utilization, yield formation, and water productivity (WP) in dryland wheat systems, a three-year split-plot field experiment (2018-2021) was designed to compare RP against flat planting (FP) under semi-arid rainfall variability. Results showed that RP improved rainwater infiltration into deeper soil layers, increasing soil water storage by 4.3-8.0 % at jointing and elevating soil water use rate by prioritizing deep-layer extraction during critical growth stages. RP combined with optimized N rates achieved the highest grain yield (25.9 %, 15.3 %, and 10.8 % increases in dry, normal, and wet years) and WP by harmonizing water-N synergies. Enhanced post-anthesis water extraction from 160-200 cm layers under RP significantly boosted dry matter accumulation. Correlation analyses revealed that spike number in dry years correlated with pre-anthesis water use in the 80-160 cm layer (P < 0.01), kernels per spike in normal years aligned with balanced pre-/post-anthesis allocation across 0-200 cm (P < 0.05), and 1000-grain weight in wet years depended on post-anthesis extraction from 160-200 cm (P < 0.01), synergistically driving yield gains. RP integrated with adaptive nitrogen thresholds (90-180 kg ha-1) is recommended to stabilize yields and maximize WP in rain-fed systems. This strategy provides a scalable pathway to strengthen climate resilience and sustainable resource utilization in water-limited agroecosystems.