In order to seek a reasonable nitrogen application system suitable for high-yield and high-quality production of maize in arid areas, this study focused on the effects of reducing nitrogen application under the condition of returning green manure to the field on maize grain yield and quality, with a view to providing a theoretical basis for the regional development of nitrogen-saving, efficiency-enhancing, high-yield and high-quality agricultural production models.

Field experiment were conducted at the Wuwei Oasis Agricultural Experiment Station from 2020 to 2022, and different nitrogen reduction rates were investigated under the condition of green manure returned to the field (Green manure retention with nitrogen reduction 0%, N100, 360 kg N·hm^-2; Green manure retention with nitrogen reduction 10%, N90, 324 kg N·hm^-2; Green manure retention with nitrogen reduction 20%, N80, 288 kg N·hm^-2; Green manure retention with nitrogen reduction 30%, N70, 252 kg N·hm^-2; and Green manure retention with nitrogen reduction 40%, N60, 216 kg N·hm^-2) on maize agronomic traits, yield components and grain quality.

Compared with the N100 treatment, the N80 treatment ensured that maize plant height, stem diameters, and dry weight did not decrease, while the N70 treatment reduced them by 8.8%, 11.3%, and 16.4%, respectively, and the N60 treatment reduced them by 10.6%, 12.9%, and 21.3%, respectively. Among the yield components, there was no significant difference in maize bare top length among treatments; ear length, row number per ear, kernel number per row, and ear numbers under N100, N90, and N80 treatments were no significant difference too, but they were all significantly higher than those under N70 and N60 treatments. In addition, N80 treatment had the advantage of ensuring that the maize grain protein content was not reduced and fat content was increased while ensuring that maize yield was not reduced. And this system helped to reduce the amount of nitrogen accumulation in maize stems and leaves, and increased the amount of nitrogen accumulation in maize grain. Mantel test analysis revealed that maize grain yield, protein content, and fat content exhibited significant positive correlations (P<0.05, Mantel’s r>0.25) with nitrogen application rate, grain nitrogen accumulation, plant height, stem diameter, dry weight, ear length, and row number per ear. However, no significant correlations were observed with ear height, bare top length, or kernels number per row. Grey correlation analysis further showed that the ear numbers, plant dry weight and row number per ear were the key factors affecting maize kernel yield.

In the context of sustainable agriculture, reducing nitrogen by 20% under the condition of returning green manure to the field (288 kg N·hm^-2) could be used as a reasonable nitrogen management system for developing nitrogen-saving and input-reducing, high-yield and high-quality agriculture in arid areas.

In order to provide the theoretical basis for the development of high-yield and high-efficiency maize production technology in this area, the characteristics of dry matter accumulation and distribution and the response of grain yield to the return of green manure to the field combined with nitrogen reduction were analyzed in the oasis irrigation area.

The field experiment was carried out in Hexi Oasis Irrigation Area, Gansu Province from 2020 to 2021. The combination of green manure returning to the field and different nitrogen reduction ratios (green manure combined with nitrogen reduction 0%, N100; green manure combined with nitrogen reduction 10%, N90; green manure combined with nitrogen reduction 20%, N80; green manure combined with nitrogen reduction 30%, N70; green manure combined with nitrogen reduction 40%, N60) on the distribution of dry matter accumulation in maize and impact on production.

After the jointing stage, the aboveground dry matter accumulation under N80 and N90 treatments was significantly higher than that of N70 and N60 treatments. At the mature stage, the aboveground dry matter accumulation under N80 increased by 13.3%-23.2% compared with N70 and N60 treatments, and N90 was higher than N70 and N60 treatments. Compared with the N70 and N60 treatments, the maximum growth rate and average growth rate of the aboveground dry matter under N80 were significantly increased by 9.5%-21.2% and 13.0%-23.2%, respectively; N90 significantly increased by 10.2%-21.8% and 13.9%-23.7% compared with N70 and N60 treatments, both of which effectively delayed the decrease of aboveground dry matter accumulation rate of maize from silking stage to grain filling stage. Compared with N70 and N60, the maximum growth rate of dry matter under N80 treatment was 2.44 d and 2.77 d earlier than that under N70 and N60, respectively, and N90 was 1.92 d and 2.3 d earlier than the N70 and N60 treatments, respectively. N80 and N90 promoted the distribution of dry matter in the ears of maize, and effectively increased the contribution rate of dry matter transport before flowering to grain dry matter accumulation. At the same time, the post-flowering dry matter accumulation under N80 increased by 12.2% and 20.4% compared with N70 and N60 treatments, respectively. Compared with the N70 and N60 treatments, the post-flowering dry matter accumulation under N90 was increased by 12.4% and 20.5%, respectively, and the difference was significant. There was no significant difference in maize grain yield among N100, N90, and N80 treatments, but the maize grain yield under N80 increased by 16.8% and 27.4%, respectively. Compared with N70 and N60 treatments, the yield under N90 treatment increased by 17.4% and 27.9%, respectively, with significant differences.

The return of leguminous green manure to the field combined with 10% and 20% nitrogen reduction treatments increased the aboveground dry matter accumulation and accumulation rate of maize, promoted the distribution of dry matter in the ears at maturity, and improved the pre-flowering dry matter transport on grain dry matter. The cumulative contribution rate could be used as the recommended nitrogen application method for high maize yield in oasis irrigated areas.