Abstract: 【Objective】To clarify the effects of nitrogen fertilization operation on maize yield and nitrogen utilization efficiency under drip irrigation in Tumochuan plain of Inner Mongolia,and explore the feasibility of using the nitrogen nutrient index as monitoring index to diagnose the nitrogen nutrient status of maize under drip irrigation with water and fertilization integration in Tumochuan plain.【Methods】The nitrogen nutrient content of mazie under 3 nitrogen fertilization rates（0,270,360 kg/hm²）and 3 and 5 nitrogen fertilization rates during the whole growth period were tested in Tumed Right Banner of Baotou City and Tumed Left Banner of Hohhot City in Inner Mongolia from 2022 to 2023. The yield and nitrogen utilization efficiency of maize were studied by using variance analysis and statistical modeling. The changes of canopy nitrogen concentration and aboveground biomass were analyzed and construct a critical nitrogen concentration dilution curve model.【Results】Increasing the rate and times of nitrogen application could significantly increase ear number,grain number per ear and 1 000-grain weight of maize,thus increasing yield. In addition,increasing nitrogen application times could significantly improve nitrogen utilization efficiency of maize（P<0.05）. Nitrogen application rate increased from 270 kg/hm² to 360 kg/hm²,and the average annual yield increased by 5.79%. Nitrogen application times increased from 3 times to 5 times,and the average annual yield and nitrogen utilization efficiency increased by 3.15% and 22.25%,respectively. The critical nitrogen concentration dilution curve of maize for drip irrigation in Tumochuan plain is N_c=3.36W^-0.22,R²=0.94,P<0.05,and the validation accuracy RMSE,NRMSE and MAE were 0.40%,11.50% and 0.20%,respectively. The stability of the model was good.According to the model calculation,when the nitrogen application rate was 270 kg/hm²,the corresponding suitable nitrogen application times were 5 times,and the ratio of 15∶25∶35∶15∶10 was applied at 4 leaf extension stage,8 leaf extension stage,12 leaf extension stage,silking stage and milking stage,respectively,the mazie yield was the best,was 14.09 t/hm². In this area,the nitrogen fertilization requirements at jointing stage,9 leaf extension stage,12 leaf extension stage,silking stage and milking stage were -3.42 to 15.29,-16.80 to 22.90,-26.86 to 62.32 and -54.65 to 85.14 and -48.18 to 111.80 kg/hm².【Conclusion】Appropriate increase of nitrogen application rate and nitrogen application times can significantly improve maize yield and nitrogen utilization efficiency in Tumochuan plain of Inner Mongolia. The critical nitrogen concentration dilution curve model of maize under drip irrigation in Tumochuan plain of Inner Mongolia can effectively identify the nitrogen nutrient status of maize plants from the jointing stage to the milking stage and calculate and recommend the appropriate fertilization application rate,so as to realize the on-demand operation of maize growth.

Key words: Tumochuan plain, Maize under drip irrigation, Critical nitrogen concentration dilution curves, Nitrogen nutrient index, Nitrogen requirement