Tuber yield and processing quality response of French fried potatoes to nitrogen fertilization

Nitrogen (N) is an important factor that influences potato production; appropriate N fertilizer management can optimize tuber yield and quality and thus reduce the risk of environmental N losses. The present study aimed to evaluate the effects of different nitrogen (N) application rates (0, 75, 150, 225, 300, and 375 kg ha-1) on the total tuber yield, marketable yield, dry matter content, reducing sugar content, sucrose content of tuber, and fry color index of two potato cultivars (Kennebec and Shepody) in 2016 and 2017. N supply significantly affected tuber yield and processing quality, but these effects depended on the year and/or cultivar. The results indicated that low (75 kg ha-1) and medium-N application rates (150 or 225 kg ha-1) had a positive effect on tuber yield and processing quality; however, high-N application rates (300 and 375 kg ha-1) resulted in lower yield and poor quality. Total and marketable yields responded quadratically to N, and they were optimized at 150 kg ha -1 for Kennebec and 225 kg ha-1 for Shepody in both the years. The processing quality of tubers also responded quadratically with increasing N application rates. The optimal range of N application was approximately 145-185.83 kg ha-1 for Kennebec and approximately 93.44-288.67 kg ha-1 for Shepody according to the processing quality standards of French fried potatoes in China. To achieve the goals of high yield and high quality, N application rates should be 150 kg ha-1for Kennebec and 225 kg ha-1 for Shepody.