Objective We studied the effects of nitrogen application rates on photosynthetic parameters and photosynthetic product accumulation and transportation characteristics of potato, and explored the relationships between yield formation parameters and photosynthetic characteristics, aiming to propose an appropriate nitrogen application rate for potato production in the mountainous areas of southern Ningxia.

Methods The experiment was conducted in Haiyuan County, Ningxia, from 2019 to 2020, using ‘Qingshu No. 9’ as the test material. A randomized block design was setup, with four nitrogen treatments: 0 kg/hm² (N0), 75 kg/hm² (N1), 150 kg/hm² (N2), and 225 kg/hm² (N3). This design facilitated the analysis of the trends in potato photosynthetic characteristics, population growth, and yield across different nitrogen application rates.

Results At 45 days after potato flowering, the leaf area index (LAI), net photosynthetic rate (Pn), stomatal conductance (Gs), and transpiration rate (Tr) for potatoes treated with N2 showed increases of 29.91%, 31.56%, 44.57% and 44.82%, respectively, compared to N0. Additionally, these parameters increased by 6.55%, 2.20%, 15.16%, and 13.39% compared to the N3 treatment. The N2 treatment was found to optimize the LAD, CGR, and NAR of the potatoes. Specifically, the maximum dry matter accumulation rate (Vmax) and the growth amount at Vmax (Wmax) in N2 treatment were 22.37% and 15.41% higher than those in N0 treatment, and 7.95% and 12.79% higher than those in N3 treatment, respectively. Among the four nitrogen application rate treatments, the potato yield and commercial potato rate in the N2 treatment achieved the highest values. A quadratic equation was fitted to describe the relationship between yield and nitrogen application rate, indicating that the economically optimal nitrogen application rates were 188 kg/hm² in 2019 and 163 kg/hm² in 2020. Pearson correlation analysis shows that potato yield was significantly or extremely significantly positively correlated with Pn, Ci, Gs, Tr, LAI, LAD and CGR. The photosynthetic parameters were positively correlated with Wmax and Vmax, but negatively positively correlated with Tmax and the active period of dry matter accumulation (D). Further principal component analysis of potato yield, yield performance indicators, and photosynthetic parameters indicated that the comprehensive scores for each treatment over the two years were ranked as follows: N2>N3>N1>N0.

Conclusions Reasonable nitrogen application significantly improves potato population photosynthetic parameters and growth rate, increases photosynthetic product accumulation and post-anthesis dry matter accumulation, thereby jointly promoting potato yield formation. Controlling the nitrogen application rate in arid areas at 150 kg/hm² will help maintain potato yield performance parameters and photosynthetic parameters within an appropriate range, and improve the accumulation and transport of photosynthetic products, thereby laying the foundation for potato yield formation. The nitrogen application rate of 150 kg/hm² can be used as the recommended nitrogen application rate for green and efficient cultivation of potatoes in the semi-arid area of northwest China.