Estimating foliar nitrogen in Eucalyptus using vegetation indexes

Abstract

Nitrogen (N) has commonly been applied in Eucalyptus stands in Brazil and it has a direct relation with biomass production and chlorophyll content. Foliar N concentrations are used to diagnose soil and plant fertility levels and to develop N fertilizer application rates. Normally, foliar N is obtained using destructive methods, but indirect analyses using Vegetation Indexes (VIs) may be possible. The aim of this work was to evaluate VIs to estimate foliar N concentration in three Eucalyptus clones. Lower crown leaves of three clonal Eucalyptus plantations (25 months old) were classified into five color patterns using the Munsell Plant Tissue Color Chart. ).

Nondestructive Estimation of Leaf Nutrient Concentrations in Eucalyptus Plantations

“…The relationship between N and leaf reflectance is very strong in practically all VIS region (Figure 4). Therefore, in the literature, indices are able to estimate the N concentration in the blue wavelength region (Hansen and Schjoerring, 2002) and in the green, red and red edge regions (Oliveira et al, 2017). In this study, better results were found using combinations of red edge wavelength regions ( Figure 5).…”

“…The increase of reflectance in the VIS region is mainly due to a reduction in chlorophyll concentration, triggered by the lowering of these nutrient concentrations (Al-Abbas et al, 1974;Adams et al, 2000). Consequently, with an increase of reflectance in the visible region there is a decrease in the intensity of the leaf color (Ponzoni and Gonçalves, 1999;Ayala-Silva and Beyl, 2005;Oliveira et al, 2017). Thus, the reduction of the intensity of the green coloration of Eucalyptus leaves can be verified through a deficiency in these nutrients with evolution of the characteristic symptoms for each nutrient (Dell, 1996).…”

“…Determination of LNCs is traditionally performed using destructive procedures, requiring laboratory chemical analysis, specialized equipment, and skilled labor. However, technological advances in recent years have made it possible to analyze LNC using nondestructive methods (Pimstein et al, 2011;Mahajan et al, 2016;Oliveira et al, 2017). Spectral analysis techniques, using a variety of sensors, have enabled crops to be managed using non-destructive methods (Ustin et al, 2009;Ollinger, 2010;Schlemmer et al, 2013), and the technology could be extended to tree plantations (Stein et al, 2014;Oliveira et al, 2017).…”

“…Currently, several indices are used to quantify the relationships between reflectance in the VIS and NIR regions and LNCs. However, such implementation has been limited to estimates of leaf pigments (eg, Gitelson et al, 2003;2006; and nitrogen (N, eg Fitzgerald et al, 2010;Schlemmer et al, 2013;Oliveira et al, 2017). Deficiencies in nutrients other than N can alter plant metabolism and consequently a leaf's reflectance (Mariotti et al, 1996;Mahajan et al, 2014).…”

Early detection of plant diseases using spectral data

“…It is portable and non-destructive of the material being measured. Most of this work tends to be be focused on determining the chlorophyll levels of the plant [13,14]. In this study we used this miniature leaf spectrometer for data collection.…”