Abstract: 【Objective】 The problem for film-mulched maize in the oasis irrigation region was an advanced N requirement and leads to the insufficient supply of N at late growth stages. In this study, the effect of topdressing nitrogen fertilizer on intercropped maize photosynthetic physiological characteristics and grain yield was studied, to reveal the photosynthetic mechanism of intercropped maize grain yield advantage in the experimental area. 【Method】From 2019 to 2021, maize were used as experimental materials in Hexi Oasis Irrigation. The split-plot experiment design was adopted, among which pea/maize intercropping and maize monoculture were the main factors, and three N fertilizer postponing application (postponing ration 20%, 10%, and traditional practice) were the secondary factors. The field experiment was studied the photosynthetic physiological characteristics and yield performance of maize under N fertilizer postponing application and intercropping pattern. 【Result】The results demonstrated that the grain yield of intercropped maize in the treatment postponing of application of 20% and 10% of N was increased by 28.5% and 13.8% and biomass yield by 23.8% and 12.5% compared with traditional N management practices, respectively. Similarly, compared with traditional N management practices, the grain yield of sole maize in the treatment postponing of application of 20% and 10% of N was also increased by 29.7% and 13.3% and biomass yield by 19.6% and 10.3%, respectively. Compared with the monoculture maize, intercropping can increase the grain yield by 33.2%-35.1% and biomass yield by 26.8%-31.5% under the same area. Furthermore, the treatment postponing of application of 20% and 10% of N increased the population grain yield of intercropping pattern by 27.2% and 12.9% compared with the traditional N management practices. The results showed that intercropping pattern can increase the grain yield of maize compared with the sole pattern and the N fertilizer postponing application boost the improvement of grain yield in the intercropping system compared with the traditional N management practices. During the whole growth periods, intercropping increased the net photosynthetic rate, stomatal conductance, transpiration rate, and decreased intercellular CO₂ concentration. Compared with traditional N management, the net photosynthetic rate the in the treatment postponing of application of 20% and 10% N was increased by 12.8% and 6.0%, the stomatal conductance by 14.0% and 6.9%, the transpiration rate by 20.5% and 9.5%, and intercellular CO₂ concentration was decreased by 29.8% and 13.1%, respectively. The SPAD value under the treatment postponing of application of 20% and 10% N was increased by 7.5% and 3.7%. The principal component analysis results showed that the N fertilizer postponing application and intercropping pattern can increase the grain yield via boosting the net photosynthetic rate, the stomatal conductance, the transpiration rate, and leaf SPAD value, and decreasing intercellular CO₂ concentration. 【Conclusion】The N fertilizer postponing application 20% treatment (36 kg·hm^-2 N fertilizer was topdressing at maize jointing stage and 108 kg·hm^-2 at 15 d post-silking stage) had the advantage of improving the photosynthetic characteristics of intercropped maize, thereby boosting the grain yield improvement.

Key words: maize, pea/maize intercropping, physiological characteristics, N fertilizer postponing application, intercropping