Abstract: A split plot experiment was conducted to study the effects of supplemental irrigation and nitrogen (N)- and phosphorus (P) fertilization on the soil water utilization, Nuptake, and grain yield of Triticum aestivum on loess tableland.   In the study year, supplemental irrigation and N- and P fertilization increased the grain yield of T. aestivum by 0-24.6% and 134.1%-240.2%, respectively. Nitrogen fertilization was the main factor in improving the grain yield of T. aestivum, while supplemental irrigation and P fertilization had little effects. Supplemental irrigation and N fertilization increased the water consumption by T. aestivum significantly. Supplemental irrigation decreased the consumption of soil water to some extent, whereas N- and P fertilization increased the soil water consumption significantly. Supplemental irrigation decreased the water use efficiency (WUE) by 0.2-2.3 kg·mm^-1·hm^-2, compared with rain-fed treatment, but the difference was not significant. Nitrogen- and P fertilization increased the WUE by 4.0-7.2 kg·mm^-1·hm^-2, being significantly higher than the control (CK). The N uptake by T. aestivum  increased significantly with increasing N application rate, and the increment was 26.9-33.4 kg N·hm^-2and 60.9-66 kg·hm^-2 under low and high N application rates, respectively, compared with CK. Supplemental irrigation promoted the allocation of absorbed N in the aboveground parts of T. aestivum. Supplemental irrigation combined with high fertilization rates of N and P could obtain high yield and higher WUE. In the years with adequate soil moisture for sowing, the key factor affecting the grain yield, WUE, and N absorption of T. aestivum on loess tableland was the N fertilization rate.

Key words: River continuum characteristics, Xiangxi River, Epilithic algae