Abstract: To investigate the effect of polyaspartic acid-chitosan (PAC) on photosynthetic characteristics, nitrogen use efficiency, and yield of spring foxtail millet under the background of one-time basic fertilizer application, an experiment following split plot design was conducted using foxtail millet varieties of “Zhangzagu 13” (Z13) and “Huayougu 9” (H9) in Gongzhuling Experimental Station of Chinese Academy of Agricultural Sciences in 2020 and 2021. PAC and different nitrogen application levels were main treatment and secondary treatment, respectively. There were six nitrogen application levels (0, 75, 112.5, 150, 225, and 337.5 kg·hm^-2). The results showed that PAC improved apparent efficiency of applied nitrogen for both foxtail millet varieties under the same nitrogen application level. The leaf area index and SPAD value of flag leaf in 0-40 days after anthesis were higher than those of the control. PAC application increased photosynthetic rate, transpiration rate, and conductance to H₂O, but significantly decreased intercellular CO₂ concentration of flag leaf at anthesis and mid-filling stage, which could promote dry matter accumulation and yield. The yield of Z13 was increased by 11.24%-21.55% in 2020 and 8.65%-14.22% in 2021, and that of H9 was increased by 5.53%-15.75% and 10.43%-16.17% in 2020 and 2021, respectively. PAC application effectively relieved nitrogen deficiency and plant premature senescence resulted from one-time basic fertilizer application during the late growth period of foxtail millet, and reduced nitrogen loss caused by low nitrogen use efficiency. Therefore, PAC combined with nitrogen fertilizer application could be used as a green, high-yielding, and high-efficiency cultivation technique in foxtail millet production in China.

Key words: foxtail millet, polyaspartic acid-chitosan, photosynthetic characteristics, nitrogen use efficiency, yield, one-time basic fertilizer application.