Abstract:

The dynamics of potato canopy growth are closely associated with the accumulation of plant dry matter and the formation of tuber yield. To explore the potential of low-cost unmanned aerial vehicle（UAV）RGB imagery for rapid，non-destructive，and accurate quantification of field potato growth under different nitrogen management conditions and for predicting tuber yield，an experiment was conducted using the potato cultivars‘Shepody’and‘Zhongshu 18’. In this study，treatments included two forms of nitrogen（nitrate and ammonium nitrogen）applied at three different rates（0，150，and 300 kg · hm^-2）. UAV RGB imagery collected during 2022 and 2023 was used to extract the average plant height and canopy cover of each plot，and a canopy development model was constructed for the entire growth season. Furthermore，at key growth stages，measurements were taken for natural plant height and total plant dry mass，and tuber yield was determined at harvest. The results showed that：（1）The accuracy of extracting plant height from experimental plots using RGB imagery was affected by the growth stage. Within a given growth period，the linear correlation between the average plant height derived from the imagery and the actual plant height became stronger as the plants grew taller. Specifically，during the starch accumulation stage，the coefficient of determination was 0.91 in 2022 and 0.81 in 2023. Furthermore，ammonium nitrogen demonstrated a greater effect in enhancing both plant height and canopy cover than nitrate nitrogen.（2）Different nitrogen management practices had varying effects on the key parameters of the potato canopy development model. Firstly，the application of nitrogen fertilizer significantly increased the maximum canopy cover，with the most pronounced effect observed for the treatment of 150 kg · hm^-2 ammonium nitrogen，followed by 300 kg · hm^-2 ammonium nitrogen，300 kg · hm^-2 nitrate nitrogen，150 kg · hm^-2 nitrate nitrogen，and the control. Although no significant differences were found in the canopy senescence time among all treatments，the use of ammonium nitrogen，particularly at an application rate of 150 kg · hm^-2，significantly reduced the thermal days required for the plants to reach maximum canopy cover. Furthermore，the total integrated area under the potato canopy development curve was significantly increased with ammonium nitrogen treatments，and the treatment with ammonium nitrogen at 300 kg · hm^-2 significantly extended the above-ground growth period.（3）The integrated area under the canopy development curve reflects the cumulative interception of photosynthetically active radiation（R² > 0.99）. This parameter is significantly and positively correlated with total plant dry mass，with R² of 0.90 in 2022 and 0.87 in 2023. Moreover，the integrated area under the canopy development curve during the tuber bulking stage showed the strongest linear correlation with tuber yield，with a Pearson correlation coefficient of 0.82. In conclusion，the canopy development model constructed using RGB imagery accurately quantified the dynamics of canopy growth and dry matter accumulation in field-grown potato plants throughout the entire growing season，thereby providing a robust scientific basis for yield prediction and the optimization of nitrogen management strategies.

Key words: potato, nitrogen, RGB imagery, canopy development model, dry matter accumulation, yield