Effects of suitable fertilizer-N application rate and planting density on increasing yield, water and nitrogen use efficiency of winter wheat

The ridge film and furrow sowing model has been widely used in the arid region of northwest China, in order to solve the problems of low yield , water and nitrogen use efficiency of winter wheat caused by drought, and unreasonable nitrogen application rate and planting density in northwest China, we explored the optimal nitrogen fertilizer and density management for high yield and efficient use of water and nitrogen of winter wheat in the ridge mulching and furrow sowing mode. Three density gradients of 150 kg/hm² (D1), 187.5 kg/hm² (D2) and 225 kg/hm² (D3) and three nitrogen application rate of 180 kg N/hm² (N1), 270 kg N/hm² (N2) and 360 kg N/hm² (N3) were set in the experiment. In a two-year field experiment (2021-2022 and 2022-2023), taking “Xiaoyan 22” as the test variety, to study the effects of different nitrogen and density treatments on the physiological growth, aboveground dry matter, yield, water and nitrogen use efficiency of winter wheat. Study the following conclusions are obtained: leaf area index (LAI) and aboveground dry matter accumulation showed a parabolic trend with the increase of nitrogen application rate or planting density, compared with local conventional nitrogen and density treatment (D1N3), reasonably increasing planting density and decreasing nitrogen application could increase LAI at the tasseling stage, and the maximum dry matter accumulation and accumulation rate by 147.25% and 65.29%. With the increase of soil depth, the soil moisture content increased at jointing stage, but decreased then increased at heading stage and filling stage. The average soil water content of 100 cm soil layer in 2 years was the highest in D3N3 and D1N3, respectively. Chlorophyll content reaches the maximum at heading stage, the suitable nitrogen and density management increased the chlorophyll content by 0.53%-31.25%. The interaction between nitrogen fertilizer and density had significant (P＜0.001) effects on yield, water and nitrogen use efficiency. Reasonable density and nitrogen management measures are conducive to the increase of yield and water and nitrogen use efficiency. Excessive nitrogen application rate or excessive planting density had certain inhibitory effects on crop growth. With the increasing of planting density or nitrogen application, the yield and water use efficiency (WUE) showed a tendency of increasing and then decreasing, and the yield reached the maximum in the D2N2 treatment, with a two-year average of 11911.93 kg/hm². Based on the regression model, comprehensive evaluation of yield, WUE and NPFP, the optimization conditions were 95% of the maximum value of yield and WUE, 85% of the maximum value of NPFP, the combination pattern of planting density of 180.45-190.04 kg/hm² and nitrogen application rate of 201.66-256.67 kg/hm² was finally determined as the nitrogen and density management measures for high yield and nitrogen efficient utilization of ridge mulching and furrow sowing winter wheat, it realized the synergistic improvement of yield and resource utilization efficiency to the maximum extent. The results of the study can provide practical guidance and theoretical basis for the high yield and efficiency cultivation of winter wheat in Northwest of China.