Objective  Varied N levels for fertilization were applied to determine the effects on the morphological and physiological characteristics of the Juglans regia L. rootstock seedlings from two provenances in Xinjiang.

  Methods  Juglans regia L. rootstock seedlings from provenances at Aksu and Hotan were treated with varied levels of N fertilizer, and the morphology, biomass, photosynthetic characteristics, and soluble sugar content in leaves of the seedlings determined.

  Results  The various evaluation indicators tended to increase initially and followed by a decline upon increasing N but responded differently between the seedling specimens from the two localities. Under 10−15 g·a⁻¹·plant⁻¹ application rates, the plant height peaked at 95.27 cm and 72.07 cm, while the total root volume at 1 249.75 cm³ and 928.01 cm³, respectively, for the Juglans regia L. plants from the two sources. The net photosynthetic rates for them increased with N to arrive at a maximum of 12.725 1 μmol·m⁻²·s⁻¹ and 12.357 3 μmol·m⁻²·s⁻¹, respectively, under the 10 g·a⁻¹·plant⁻¹ fertilization. Further increases on N caused a gradual decline on the net photosynthetic rate. According to the comprehensive evaluation, the morphological characteristics and physiological characteristics of Juglans regia L. rootstock seedlings in the two provenances with nitrogen application at 10−15 g·a⁻¹·plant⁻¹ showed the optimal characters.

  Conclusion  Over all, the Juglans regia L. rootstock seedlings from the two provenances performed well morphologically and physiologically under the applications of 10−15 g·a⁻¹·plant⁻¹. In that range, Aksu walnut exhibited a greater N utilization ability than its counterpart.