Abstract: To improve wheat yield, fertilizer utilization efficiency, and economic benefits, a field experiment was conducted with seven treatments, including no fertilizer (CK), conventional fertilization (CF), and 10%, 20%, 30%, 40%, and 100% substitution of chemical fertilizer with organic fertilizer with equivalent nitrogen (10% OM to 100% OM). The effects of different substitution ratios on wheat yield and its components, nitrogen fertilizer utilization efficiency, and soil physicochemical properties were systematically evaluated. The results showed that partial substitution treatments increased spike number, grains per spike, 1000-grain weight, and wheat yield. The highest wheat grain yield of 570.3 kg/667 m; ² was achieved under the 20% OM treatment. The total nitrogen, total phosphorus, and total potassium contents in wheat grain under the 10% OM to 40% OM treatments were higher than those under the CF treatment. The partial factor productivity of nitrogen fertilizer, agronomic efficiency of nitrogen fertilizer, and nitrogen harvest index reached their highest values under the 20% OM treatment, while the apparent nitrogen fertilizer utilization efficiency was the highest under the 30% OM treatment. Compared with the CF treatment, the application of organic fertilizer generally increased the contents of soil organic matter, total nitrogen, available phosphorus, and available potassium, with all these indicators reaching their peak under the 100% OM treatment. Soil organic matter and total nitrogen significantly promoted wheat grain yield and its components. Considering wheat yield, nitrogen fertilizer utilization efficiency, and soil physicochemical properties comprehensively, a substitution ratio of 20% to 30% for organic fertilizer with equivalent nitrogen was found to be appropriate, which contributed to wheat yield increase, improved nitrogen fertilizer utilization efficiency, and enhanced soil quality.

Key words: substitution ratio, organic fertilizer with equivalent nitrogen, wheat, yield, nitrogen fertilizer utilization efficiency