| From 2019 to 2021, a re\|split plot design was used to study the effects of nitrogen fertilizer combined with biochar and urease inhibitor on crop yield and nitrogen uptake and utilization in summer maize\|winter wheat rotation system. Three factors of nitrogen fertilizer, biochar and urease inhibitor were set up. The main treatment was set up with five nitrogen levels: 0, 75, 150, 225 kg·hm-2 and 300 kg·hm-2, and the secondary treatment was set up with two biochar levels: 0 t·hm-2 and 7.5 t·hm-2. Under the secondary treatment, two urease inhibitor levels of 0% and 2% were used. The results showed that the application of biochar significantly increased the yield, plant nitrogen uptake, apparent nitrogen use efficiency (ANUE), nitrogen harvest index of summer maize and winter wheat and aboveground biomass of summer maize, which were 4.4% and 2.9%, 2.3% and 3.0%, 25.8% and 13.5%, 4.9% and 6.1%, 4.5% higher than those without biochar application, respectively. Nitrogen fertilizer combined with biochar significantly increased the yield of summer maize and winter wheat, plant nitrogen uptake and ANUE, and there was a significant interaction between nitrogen fertilizer and biochar. The application of urease inhibitors significantly increased the nitrogen uptake and ANUE of summer maize plants, which were 1.5% and 3.0% higher than those without urease inhibitors, respectively. Nitrogen fertilizer combined with urease inhibitor could increase nitrogen uptake and ANUE of summer maize, but there was no significant interaction between nitrogen fertilizer and urease inhibitor. Nitrogen fertilizer combined with biochar and urease inhibitor significantly increased the yield, plant nitrogen uptake and ANUE of summer maize and winter wheat, with an average increase of 10.0% and 4.2%, 5.4% and 3.4%, 11.0% and 6.2%, respectively, compared with N fertilization alone, but there was no significant interaction between nitrogen fertilizer, biochar and urease inhibitor. In summary, nitrogen fertilizer alone combined with biochar increased the yield of summer maize and winter wheat and its absorption and ANUE, and the effect was better than that combined use of biochar and urease inhibitor. Nitrogen fertilizer alone with urease inhibitor had a certain effect on improving the absorption and utilization of nitrogen fertilizer in summer maize. |