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

trient concentration in the leaves (Beaufils, 1973). Those dual ratios represent the minimum expression for nutriIn this study, we evaluated the potential of reflectance and fluoresent interactions. Parent and Dafir (1992) developed a cence for the detection of the Compositional Nutrient Diagnosis (CND) N index (IN). The CND reflects nutrient deficiencies as well new indicator of plant nutritional status: the CND. The as nutrient interactions, contrary to conventional methods of nutrient CND not only evaluates the foliar composition in nutristress detection. Potato plants (Solanum tuberosum L. cv. Superior) ents, but it also estimates the interactions that might were grown in a greenhouse, and three different nutrient deficiencies appear between any nutrient included in the plant (Par(K, Mg, and N) were induced at three levels and compared with a ent and Dafir, 1992). The CND is based on the Composicontrol receiving a complete nutrient solution. Nitrogen deficiency tional Data Analysis (Aitchison, 1986), and its first asinduced a significant biomass reduction compared with control plants sumption is to consider the analyzed leaf as a whole or whereas no significant effect was observed for K or Mg treatments. a simplex; therefore summing up all its constituents will Foliar analyses were realized to compute the CND_r 2 using the CND. equal 100%. The computation of the CND_r 2 of a diagThe ANOVA conducted on CND_r 2 and IN showed significant differnosed specimen involves using the geometrical mean of ences only between N-deficient and control plants. Using a canonical discriminant analysis over reflectance and fluorescence indices, it was all nutrients: each nutrient content is compared with all possible to correctly classify 96.6% of potato plants in its correspondothers, thus providing information on nutrient interacing IN class. A new Multivariate Indicator of Nitrogen Imbalance tions and leading to the identification of nutrient imbal(MINI) was developed using the canonical variable computed from ances. The CND_r 2 has a chi-square distribution (Khiari reflectance and fluorescence indices. The MINI can detect almost et al., 2001a). 70% of the N-deficient plants and more than 90% of the N-sufficient Up to now, nutrient diagnosis techniques have been plants. This indicator allows a rapid data acquisition and handling based on destructive analyses of leaves’ mineral conand provides deficiency detection within the time-window for plant tents. Remote sensing techniques such as fluorescence response to recovery fertilization. and reflectance could lower the costs and accelerate the acquisition, handling, and analysis of plant tissues and do it in a nondestructive manner. Those two techT potato crop is cultivated in more than 120 counniques respond to plants’ structural and biochemical tries worldwide with an annual production of 310 properties that are sensitive to plant nutrient status, million Mg (FAO, 2004). Potato crops are generally grown notably the content in photosynthetic pigments and pheon sandy soils and can suffer from nutrient stresses nolic compounds (Cerovic et al., 1999; Read et al., 2002; resulting from nutrient leaching or inadequate fertilizaSchuerger et al., 2003). Indeed, several studies have tion. To assure nutrient balance and improve nutrient demonstrated the possibility of detecting plant mineral management during the growing season, N and other deficiencies, especially for N, by reflectance (Adams nutrient deficiencies must be diagnosed precisely. Nutriet al., 1993; Gamon et al., 1997; Haboudane et al., 2002; ent stresses may be identified by comparing the leaves’ Vouillot et al., 1998; Zhao et al., 2003) and by UVcontent in nutritive elements with the critical threshold induced fluorescence (Apostol et al., 2003; Chappelle values for each nutrient. However, the detection of nuet al., 1984; Corp et al., 2003; McMurthey et al., 1994; trient deficiencies one by one might not reflect the real Mercure et al., 2004; Tartachnyk and Rademacher, nutritional status of the plant. Actually, there are nutri2003). To evaluate the efficiency of reflectance and/or ent interactions in plants that may interfere with the fluorescence to detect plant nutrient deficiencies, most interpretation of the results (Munson and Nelson, 1990). studies relate the remote sensing indices to the leaves’ In 1973, Beaufils developed the Diagnosis and Recompigment content (chlorophyll), the treatment induced, mendation Integrated System (DRIS) to estimate the or occasionally to biomass or nutrient content. As mennutritional status of plants by using many dual ratios tioned in Bélanger (2005), it is important to measure (N/P, N/K, N/Ca...X/Y) that are computed using the nugrowth parameters to evaluate the changes induced on fluorescence or reflectance indices. The combination of M-C. Bélanger and A.A. Viau, Laboratoire de Géomatique Agricole reflectance and fluorescence indices was suggested by et d‘Agriculture de Précision, Local 3731-A, Pavillon Casault, UniMcMurthey et al. (1994) to improve the detection of versité Laval, QC, G1K 7P4, Canada; G. Samson, Université du Québec à Trois-Rivières, Case Postale 500, Trois-Rivières, QC, G9A 5H7, nutrient deficiencies and was confirmed in a previous Canada; and M. Chamberland, Telops, 100-2600, Avenue Saint-Jeanexperiment conducted on N-, K-, and Mg-deficient poBaptiste, Québec, QC, Canada, G2E 6J5. Received 2 Feb. 2005. *Cortato plants (Bélanger, 2005). By determining the relaresponding author ([email protected]). Published in Agron. J. 97:1515–1523 (2005). Remote Sensing Abbreviations: CND, Compositional Nutrient Diagnosis: CND_r 2, Compositional Nutrient Diagnosis nutrient imbalance index; DAE, doi:10.2134/agronj2005.0040 © American Society of Agronomy day after emergence; IN, nitrogen index; MINI, Multivariate Indicator of Nitrogen Imbalance. 677 S. Segoe Rd., Madison, WI 53711 USA 1515 Published online October 19, 2005