Near Infrared Spectroscopy for Determination of Total and Exchangeable Cations in Geologically Heterogeneous Forest Soils

Abstract

Sustainable forest management requires information on a number of soil properties. Therefore fast methods of soil analysis are needed. The objective of this study was to test the ability of near infrared (NIR) spectroscopy to predict the total and exchangeable Na, K, Ca, Mg, Mn, Fe and Al, the cation exchange capacity (CEC), the base saturation (BS) and the total contents of Zn, Cu, Cd and Pb in geologically heterogeneous forest soils. The samples (n = 100) were collected from five sites covered by beech (Fagus sylvatica L.) forest stands and from four depths. The soils were analysed for total contents of Na, K, Ca, Mg, Mn, Fe, Al, Zn, Cu, Cd and Pb after pressure digestion in HNO 3 and for contents of exchangeable Na, K, Ca, Mg, Mn, Fe and Al in NH 4 Cl. The spectra were recorded between 400 and 2500 nm at 2 nm intervals. Principal components analysis revealed significant spectral differences among the samples from different sites. The global NIR models predicted well the mean values of the total contents of all cations, Zn, Pb, the exchangeable K, Mg, Fe and BS in upper (0-10 cm) and lower (10-20 cm) layers of the studied soils: the correlation coefficients (r 2) of the linear regression (measured against predicted values) varied between 0.90 and 1.00 and the regression coefficients (a) ranged from 0.94 to 1.07. The contents of Cu, CEC and the exchangeable Na, Ca and Al were predicted satisfactorily (r 2 = 0.87-0.98, a = 0.86-1.14). The global models overestimated the values of total Ca and exchangeable Ca, Mn and Fe in the lower parts of their ranges resulting in biased estimations of the means at some of the considered sites. Splitting the sample population into spectrally similar groups enabled the development of local calibrations, which improved the prediction accuracy (lower standard errors of prediction) for most of the analysed constituents and removed the bias in the estimations of exchangeable of total Ca and Ca, Mn and Fe. The obtained results indicated the usefulness of NIR spectroscopy for determination of a number of soil constituents in geologically heterogeneous forest soils.

Fast and Inexpensive Detection of Total and Extractable Element Concentrations in Aquatic Sediments Using Near-Infrared Reflectance Spectroscopy (NIRS)

“…Model quality was sufficient to distinguish between high and low values for Mehlich III extractable Mg and Mn and Ca and Mg extracted with ammonium acetate, whereas predictions were unsuccessful for the other tested elements (Mehlich III: Cu, Fe, K, P, Zn; ammonium acetate: Na, K). Better performance results for NIRS calibrations to measure exchangeable Ca, Mg and K were obtained by Zornoza et al [46] and Chodak et al [47]. This was partly related to strong correlations with the organic matter content.…”

On-line measurement of soil properties without direct spectral response in near infrared spectral range

“…The surplus of magnesium was determined by atomic absorption following the NR-SAS SOP 42/Version 1, based on the BS 7755 Section 3.12 (1996), for the determination of the potential cation exchange capacity and exchangeable cations using barium chloride buffered at pH = 8.1, which is identical to ISO 13536 (1995) (Table 3). Base saturation was calculated as the equivalent sum of major base cations (Ca ex , Mg ex , K ex and Na ex ) percentage of CEC (Chodak et al, 2004).…”

Organic substrate, clay type, texture, and water influence on NIR carbon measurements

“…These libraries are developed to represent users' geophysical region, are made up of reference soils whose constituents of interest are known, and theoretically contain representative soils within a digital library. Having a broad calibration range may allow a user to characterize heterogeneous sample sets, but often, restriction of calibration sets improves predictive ability for specific traits of interest (Chang et al, 2001;Chodak et al, 2004;McCarty and Reeves, 2000).…”