Infrared spectroscopy prediction of organic carbon and total nitrogen in soil and particulate organic matter from diverse Canadian agricultural regions

Abstract

Infrared spectroscopy has the capacity to predict soil organic carbon (SOC) and total nitrogen (TN) at local/regional scales, but no studies have been conducted to evaluate this technique at a large (cross-regional) scale in Canada. In this paper, mid-infrared (MIR) and near-infrared (NIR) spectroscopies in combination with partial least-squares regression (PLSr) were used to predict SOC and TN in whole soil and in particulate organic matter (POM) fractions on cross-regional, regional, and local scales. Both MIR-and NIR-PLSr models have well estimated SOC [coefficient of determination (R 2) = 0.79-0.92, residual prediction deviation/ratio of prediction to deviation (RPD) = 2.19-3.47], TN (R 2 = 0.70-0.92; RPD = 1.83-3.50), POM-C (R 2 = 0.76-0.96; RPD = 2.04-5.25), and POM-N (R 2 = 0.70-0.97; RPD = 1.83-5.78). The prediction efficiency of cross-regional models (R 2 = 0.90-0.96; RPD = 3.13-5.49) was similar to or better than the prediction of regional (R 2 = 0.70-0.97; RPD = 1.83-5.78) and local models (R 2 = 0.70-0.96; RPD = 1.83-5.33) and overall MIR-PLSr models (R 2 = 0.90-0.96; RPD = 1.98-3.47) yielded similar predictions for SOC and TN relative to NIR-PLSr models (R 2 = 0.70-0.92; RPD = 1.83-3.50) at cross-regional scale. Hence, it may be possible to develop MIR and (or) NIR spectral models to estimate and monitor SOC, TN, POM-C, and POM-N, and therefore, soil quality, in a rapid and cost-efficient manner across regions with diverse soil types, climate, and cropping history.

Effects of sample pretreatment and particle size on the determination of nitrogen in soil by portable LIBS and potential use on robotic-borne remote Martian and agricultural soil analysis systems

“…The total nitrogen content was determined in the different particle size fractions of the commercial topsoil using the CHN Analyser. Results varied between 1.02 and 0.32%similar to for example the range (0.1-1.2%) recently reported for a suite of Canadian agricultural soils 49 and general decreased with increasing particle size (Fig. 5).…”

Water Repellency and Hydrophobicity of Some Major Agricultural Crop Residues

“…Fine‐ground plant samples were used for mid‐infrared (mid‐IR) spectra collection with a FTIR spectrometer and mid‐IR spectral analysis with OPUS software 7.0 (Bruker Optic GmbH, Germany) as described previously (Zhang et al, 2018). Approximately 0.2 g of each plant sample was placed into a stainless‐steel sample cup and then leveled with a flat spatula.…”

Prediction of Soil Carbon Fractions Using a Field Spectroradiometer Equipped with an Illuminating Contact Probe

“…Coefficients of determination for ground POM N and C were R 2 = 0.94 and 0.97, respectively, whereas R 2 for RACH was the lowest but still an excellent fit (R 2 = 0.92). Researchers in Canada developed models for TSN, TSOC, and POM C and POM N using eight soils under varying land uses, obtaining similar coefficients of determination [20]. The ratios of the standard deviation to the standard error of cross-validation (RSC) were all above three with the exception of the ground POM N (2.84).…”

“…Measurements of reflectance in various parts of the electromagnetic spectrum, such as in diffuse reflectance Fourier transform infrared spectroscopy (DR-FTIR, 2500-10,000 nm) or less specialized measurements in the mid-infrared (MIR, 2500-25,000 nm), near-infrared (NIR, 800-2500 nm), and visible (400-800 nm) wavelength regions, are invaluable, as each technique provides information with respect to specific functional groups in plant and soil organic matter as well as edaphic properties [17][18][19][20]. Using a range of wavelengths described above, it is possible to trace the incorporation of plant material into various fractions of C and N in soils that are associated with specific and overlapping mineral fractions, such as the light fraction (organic components of soil that float on the surface of a liquid with a density in the range of 1.60 to 2.00 g cm −3 as defined by Elliott and Cambardella [21], the particulate organic matter fraction, and the resistant C fraction [19,22].…”