Objective  The paper aims to evaluate the effect of combined application of nitrogen (N) and organic fertilizer on N utilization and soil fertility of spring wheat in the semi-arid area of Loess Plateau in central Gansu.

  Method  A five-year field experiment was conducted on the wheat field of loessial soil developed from the loess parent material in the dry farming area of the Loess Plateau in Central Gansu. The dry farming spring wheat (Triticum aestivum L.) in Central Gansu was used as the research object, and the treatments included: no N fertilizer (CK) as the control, a single application of chemical N fertilizer (N, urea 228.2 kg hm⁻²), a single application of organic fertilizer (M, organic fertilizer 21.0 t hm⁻²) and chemical N fertilizer combined with organic fertilizer (NM, urea 114.1 kg hm⁻² and organic fertilizer 10.5 t hm⁻²). The N accumulation, N use efficiency of spring wheat and soil nutrition content were determined under equal N conditions.

  Result  ① Compared with N treatment, the N accumulation of spring wheat in the mature stage was increased by 15.89%, and the average N absorption rate in the whole growth stage was increased by 15.67%. The N transport amount, transport rate, and N accumulation after anthesis of spring wheat under NM treatment increased by 24.72%, 4.45% and 21.95%, respectively. The partial N productivity, N recovery rate, N agronomic utilization efficiency, and N harvest index of spring wheat in NM treatment were increased by 20.50%, 16.35%, 24.14%, and 2.07%, respectively. ② The contents of soil organic carbon and total N in NM treatment were 7.90% and 5.86% higher than those in N treatment. Except for tillering stage, the content of soil inorganic N under each treatment was NM > N > M > CK, and there was a significant difference among the treatments (P < 0.05). Compared with N treatment, the content of soil inorganic N increased by 9.66% under NM treatment in the whole growth period of wheat. ② The yield of spring wheat treated with NM was optimized, and the yield of spring wheat was higher than these of other biological factors. The yield of spring wheat under NM treatment reached 2787.13 kg hm⁻², which was 17.89% higher than that of conventional fertilization treatment (N). Through path analysis, it was found that the increase of effective panicles per hectare and 1000 grain weight was an important reason to promote wheat yield.

  Conclusion  In conclusion, under the condition of equal N amount, chemical N fertilizer combined with organic fertilizer can fertilize the soil and improve the soil N availability. In addition, simultaneous improvement of N use efficiency and yield of spring wheat under reduced fertilizer application. Thus, it is a fertilizer application method worthy of popularization in the spring wheat production in the dry farming area of central Gansu.