Possibility of using a SPAD chlorophyll meter to establish a normalized threshold index of nitrogen status in different potato cultivars

Abstract

Leaf SPAD values are thought to be an indicator of potato nitrogen (N) status; however, when making plant N diagnosis, no single threshold leaf SPAD value can be used for all potato cultivars because of cultivar variation. We conducted field experiments over 3 years to test whether the difference in SPAD values between the upper and lower leaves was consistent among potato cultivars, and whether this value responded to N application levels. The results showed cultivar affects the SPAD values of the fourth and eighth leaves (SPAD_L4 and SPAD_L8), but not SPAD_L4-8, the difference between SPAD_L4 and SPAD_L8. Moreover, the SPAD_L4-8 values responded well to N application levels. Therefore the SPAD_L4-8 could be applied as a general index of N status across different potato cultivars, and establishing a threshold SPAD_L4-8 value might be more useful in guiding N fertilization recommendations for different potato cultivars.

Keywords:

• crop N status
• potato
• chlorophyll meter SPAD
• diagnosis
• cultivars
• N recommendation

Additional information

Funding

This research was financially supported by the Innovation Team of Universities in Inner Mongolia of China (NMGIRT—A1602), the National Natural Science Foundation of China (31360502, 31760356).