Estimating olive leaf nitrogen concentration using visible and near-infrared spectral reflectance

VIS-NIR spectroscopy for estimation of Nitrogen (N) content in olive leaves was studied as a tool for efficient fertilisation in olive (Olea europaea) orchards. Olive leaf samples (cv. Barnea) were taken from orchards which had been fertilised with a wide range of N levels. Dried ground leaves, fresh ground leaves and intact leaves were tested. Reflectance measurements were taken using three spectrometers: USB-2000 for VIS-NIR (450–1000 nm) and a LIGA, and a Luminar-5030 for SWIR (1100–1700 nm). Nitrogen concentrations of the same samples were measured analytically as a reference for the spectral analyses, which were conducted by means of partial least square regression (PLSR). The best predictive model for comprehensive in-season and between-season samples (160 samples from three seasons, taken on 18 separate days) was obtained using the Luminar spectrometer using thoroughly ground dried leaves (R2 = 0.91). Classification into three N levels was evaluated and gave an overall accuracy of 0.83 with a kappa of 0.75 (substantial). Intact leaves yielded non-sufficient correlations. The results showed that leaf dehydration improves the model performance significantly and that VIS-NIR spectroscopy might be used for decision-making in fertilisation procedures. Finally, a protocol is suggested for laboratory spectral measurements.

[1]  Jacob Cohen,et al.  Weighted kappa: Nominal scale agreement provision for scaled disagreement or partial credit. , 1968 .

[2]  Eric A. Ben-David,et al.  Olive oil composition as a function of nitrogen, phosphorus and potassium plant nutrition , 2009 .

[3]  E. K. Kemsley,et al.  Potential of Fourier transform infrared spectroscopy for the authentication of vegetable oils , 1994 .

[4]  Francisca López-Granados,et al.  Assessing Nitrogen and Potassium Deficiencies in Olive Orchards through Discriminant Analysis of Hyperspectral Data , 2007 .

[5]  A. Karnieli,et al.  Rapid assessing of water and nitrogen status in wheat flag leaves , 2005 .

[6]  J. B. Magee,et al.  Predicting Concentrations of Individual Sugars in Dry Mixtures by Near-Infrared Reflectance Spectroscopy , 1981 .

[7]  T. Saaty.  The Seven Pillars of the Analytic Hierarchy Process , 2001 .

[8]  Won Suk Lee,et al.  Nondestructive Detection of Nitrogen in Chinese Cabbage Leaves Using VIS–NIR Spectroscopy , 2006 .

[9]  I. Wesley,et al.  Identification of adulterants in olive oils , 1996 .

[10]  G. G. Dull,et al.  Near Infrared Spectrophotometric Determination of Individual Sugars in Aqueous Mixtures , 1986 .

[11]  J. Shenk,et al.  Application of NIR Spectroscopy to Agricultural Products , 1992 .

[12]  M. Uceda,et al.  Olive Oil Quality Decreases with Nitrogen Over-fertilization , 2006 .

[13]  John R. Miller,et al.  Integrated narrow-band vegetation indices for prediction of crop chlorophyll content for application to precision agriculture , 2002 .

[14]  H. Gausman,et al.  Leaf Reflectance vs. Leaf Chlorophyll and Carotenoid Concentrations for Eight Crops1 , 1977 .

[15]  Francisca López-Granados,et al.  Leaf nutrient spatial variability and site-specific fertilization maps within olive (Olea europaea L.) orchards , 2004 .

[16]  Z. Schmilovitch,et al.  In-Field Assessment of Single Leaf Nitrogen Status by Spectral Reflectance Measurements , 2005, Precision Agriculture.

[17]  H. Bartsch,et al.  Olive-oil consumption and health: the possible role of antioxidants. , 2000, The Lancet. Oncology.

[18]  Y. Etzion,et al.  Determination of protein concentration in raw milk by mid-infrared fourier transform infrared/attenuated total reflectance spectroscopy. , 2004, Journal of dairy science.

[19]  J. E. Fernández,et al.  Influence of Fertigation in 'Manzanilla de Sevilla' Olive Oil Quality , 2007 .

[20]  A. Schwartz,et al.  Flowering and Fruit Set of Olive Trees in Response to Nitrogen, Phosphorus, and Potassium , 2008 .

[21]  Essex E. Finney,et al.  Determination of Moisture in Corn Kernels by Near-Infrared Transmittance Measurements , 1978 .

[22]  V. Alchanatis,et al.  Leaf nitrogen estimation in potato based on spectral data and on simulated bands of the VENμS satellite , 2010, Precision Agriculture.

[23]  R. Fernández-Escobar,et al.  Nitrogen status influence on olive tree flower quality and ovule longevity , 2008 .

[24]  Tetsuo Sato,et al.  Application of principal-component analysis on near-infrared spectroscopic data of vegetable oils for their classification , 1994 .

[25]  Ana Garrido-Varo,et al.  Parent and harvest year effects on near-infrared reflectance spectroscopic analysis of olive (Olea europaea L.) fruit traits. , 2004, Journal of agricultural and food chemistry.

[26]  J. Ryther,et al.  Nitrogen, Phosphorus, and Eutrophication in the Coastal Marine Environment , 1971, Science.

[27]  Bernhard Lendl,et al.  Determination of oil and water content in olive pomace using near infrared and Raman spectrometry. A comparative study , 2004, Analytical and bioanalytical chemistry.

[28]  C. T. Snell,et al.  Colorimetric methods of analysis : including some turbidimetric and nephelometric methods , 1948 .

[29]  Z. Schmilovitch,et al.  Determination of mango physiological indices by near-infrared spectrometry , 2000 .