Determination of a Multivariate Indicator of Nitrogen Imbalance (MINI) in Potato Using Reflectance and Fluorescence Spectroscopy

Received for publication February 2, 2005. In this study, we evaluated the potential of reflectance and fluorescence for the detection of the Compositional Nutrient Diagnosis (CND) N index (IN). The CND reflects nutrient deficiencies as well as nutrient interactions, contrary to conventional methods of nutrient stress detection. Potato plants (Solanum tuberosum L. cv. Superior) were grown in a greenhouse, and three different nutrient deficiencies (K, Mg, and N) were induced at three levels and compared with a control receiving a complete nutrient solution. Nitrogen deficiency induced a significant biomass reduction compared with control plants whereas no significant effect was observed for K or Mg treatments. Foliar analyses were realized to compute the CND_r^2 using the CND. The ANOVA conducted on CND_r^2 and IN showed significant differences only between N-deficient and control plants. Using a canonical discriminant analysis over reflectance and fluorescence indices, it was possible to correctly classify 96.6% of potato plants in its corresponding IN class. A new Multivariate Indicator of Nitrogen Imbalance (MINI) was developed using the canonical variable computed from reflectance and fluorescence indices. The MINI can detect almost 70% of the N-deficient plants and more than 90% of the N-sufficient plants. This indicator allows a rapid data acquisition and handling and provides deficiency detection within the time-window for plant response to recovery fertilization.