NIR Spectroscopy: An Alternative for Soil Analysis

• Published in: Communications in Soil Science and Plant Analysis Vol. 43; no. 1-2; pp. 346 - 356
• Main Authors: Fuentes, Mariela, Hidalgo, Claudia, González-Martín, I, Hernández-Hierro, J. M, Govaerts, B, Sayre, K. D, Etchevers, Jorge
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Philadelphia, PA Taylor & Francis Group 2012; Taylor & Francis; Taylor & Francis Ltd
• Subjects: agricultural soils; Agronomy. Soil science and plant productions; Biological and medical sciences; carbon; Chemometric predictions; chemometrics; corn; correlation; crop residues; crop rotation; Cropping systems. Cultivation. Soil tillage; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; instrumentation; least squares; Mexico; near-infrared reflectance spectroscopy; near-infrared spectroscopy; NIR; nitrogen; prediction; soil analysis; soil carbon; soil nitrogen; Soil science; Soil tillage; Soils; spectral analysis; Spectrum analysis; stable isotopes; Studies; tillage; Tillage. Tending. Growth control; Triticum aestivum; wheat; Zea mays; Mexico; Central America; America; stable isotopes; Soil tillage; soil carbon; Prediction; Nitrogen; Carbon; soil nitrogen; tillage; Reflection spectrometry; Soils; Near infrared spectrometry; Chemometric predictions; NIR; Mexico; Isotopes; Chemometrics
• ISSN: 1532-2416; 0010-3624; 1532-2416; 1532-4133
• DOI: 10.1080/00103624.2012.641471

Advances in laboratory instrumentation and chemometrics provide alternatives to traditional methods of conducting soil chemical analysis. One of these is infrared diffuse reflectance spectroscopy in the near-infrared spectral range (NIRS). Herein we report the results of a multinational study to develop useful calibrations associating NIRS spectra with laboratory-measured results for total soil carbon (C), total soil nitrogen (N), δ¹³C, and δ¹⁵N from a single soil site in Mexico subjected to zero- and conventional-tillage regimens with and without crop residues and crop rotations of maize and wheat across 16 years. Modified partial least squares regression (MPLS) was used to obtain useful NIR predictions for total soil C and N, with ratio performance deviation (RPD) values of 6.8 and 2.6, respectively. Corresponding multiple correlation coefficients (RSQs) for C and N were 0.98 and 0.85, with standard errors of prediction (SEPs) of ±0.45 g C kg–¹ and ±0.09g Nkg–¹, respectively. The generation of δ¹⁵N and δ¹³C models produced different NIR recordings in soils with and without crop residues. Application of discriminant partial least squares (DPLS) statistics to the NIR spectral data allowed us to discriminate soils with and without residues. The prediction confidence for stable isotopes was 90% (internal validation) and 94% (external validation). Modified partial least squares regression was used to estimate δ¹⁵N and δ¹³C. Ratio performance deviation, RSQ, and SEP values obtained for δ¹³C and δ¹⁵N were 2.44 and 3.57, 0.83 and 0.81, ±0.5‰ (parts per thousand) and ±0.45‰ in soils with residues and 2.5 and 3.8, 0.93 and 0.92, and ±0.2‰ and ±0.23‰ in soils without residues, respectively. Overall, results obtained with NIRS were comparable to those obtained using conventional analytical methods, a finding that has wide relevance to agricultural soils and environmental studies in tropical locations. However, further testing is necessary to confirm that the calibration models are neither site nor instrument specific.