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Soil and Landscape Science
Surface Water Hydrology
Groundwater Hydrology
Environmental Information Systems
Environmental Earth Observation
Catchment Biogeochemistry and Aquatic Ecology
Contaminant Chemistry and Ecotoxicology
Water Reuse and Environmental Process Engineering
Urban Water Systems Engineering
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 Infrared Soil Analysis Service - Routine Services
History | What is mid infrared (MIR) spectroscopy? | The strengths of the CSIRO MIR service | Predicting soil properties | Sample requirements | Partial Least-Squares (PLS) Analysis | The MIR Facility in Adelaide | Price list | Staff / Contact details Welcome to the CSIRO Infrared Soil Analysis Service, Adelaide, South Australia.CSIRO Land and Water has considerable expertise in the use of mid infrared (MIR) spectroscopy. This cost-effective technique can be used to predict a wide range of chemical and physical soil properties quickly and easily. The CSIRO Infrared Soil Analysis Service is available to industry, government, research institutes and universities on a routine basis. We also conduct research and provide fundamental information on soil chemistry, soil organic matter, and soil mineralogy for scientists around Australia. A broad range of cost-effective analytical data currently supports activities such as soil surveys, environmental monitoring and precision agriculture. HistoryMid infrared (MIR) spectroscopy was first used by the CSIRO Division of Soils in 1965, primarily for the study of soil organic matter, soil mineralogical processes and clay-organic interactions. In 1993, the potential for MIR to rapidly characterise soil organic matter was recognised by CSIRO and the multivariate method of Partial Least Squares (PLS) was applied in order to predict carbon pool concentrations in soils. The principles developed for soil organic matter were subsequently extended to the prediction of many other soil properties, and a routine soil analysis service was established within the CSIRO Analytical Service Unit in 2004. What is Mid Infrared (MIR) Spectroscopy?
The resulting MIR spectrum is determined by the nature of the soil; specific vibrational signatures can be seen for organic matter (OM) and for minerals such as quartz (sand), kaolinite and smectite (clays), carbonates (lime), gypsum, and iron and aluminium oxides. Once the equipment has been calibrated (using samples with known properties) the properties of other soils can be predicted using appropriate software (partial least squares (PLS) statistical analysis).
The strengths of the CSIRO MIR serviceThe major strengths of the CSIRO MIR service are:
The MIR method provides a very rapid and useful tool for the investigation of chemical and physical processes important in plant root growth, soil fertility, soil acidity, soil moisture retention and factors determining nutrient availability. Due to the low cost of the MIR method for soil analysis, it is ideally suited to landscape variability surveys and precision agriculture. Predicting soil propertiesMIR can predict a wide range of chemical and physical soil properties that are closely related to the bulk properties of soil (clay, organic matter, moisture content, cation capacity, mineralogy). It must be remembered that the MIR technique predicts many soil properties; it does not measure them directly. At the CSIRO Analytical Services Unit in Adelaide we can predict soil properties to the following level of precision, according to the current calibration. (Customised calibrations have been determined for some specific sites and soil types.) If samples are not typical of the current calibration soils, predictions may be less accurate. To confirm or validate the calibration, it is recommended that a small number of laboratory analyses be undertaken first – see sample requirements.) Table 1: Typical soil properties predicted by MIR
Prediction of properties at present is limited to those properties that are in equilibrium with the soil particles. The technique is not recommended for the prediction of transient available nutrients in soil (extractable nitrate, phosphorus, sulfur and micronutrients), as these occur in the soil solution around and between soil particles. CSIRO currently has calibration sets for soils that are either ground (~0.1mm) or unground (<2mm). We are always developing and improving our calibration sets. Cost can be reduced by scanning the ‘as received’ (<2mm) air-dry soil samples. Additional grinding has been found to improve prediction accuracy for some properties, but increases cost and analysis time. Interpretation of the soil variability (as described below), including spectra and written reports, would incur a further cost. Sample requirementsProspective clients should note the following sample requirements. Direct contact with CSIRO MIR laboratory staff before submitting samples is essential to ensure appropriate procedure for sample collection and treatment. Weight: 7-10g For site-specific applications, we would suggest selecting either 10% of the sample set or a minimum of 15-20 samples that describe the maximum variability of soils within a set. This can be done from either their MIR spectra or known lab data. This subset of samples could then be analysed in the laboratory, at additional cost, and used to construct calibrations, which would then be used to predict the remaining samples in the set. Alternatively the subset can be used as validation samples to confirm the predictions or adjust for slope and bias errors. This procedure reduces prediction errors for localised soil sets. For specialised calibrations, a minimum of 100 calibration samples is usually required. For these samples, laboratory data must also be supplied. Partial Least-Squares (PLS) AnalysisThe organic and mineral components of any given soil will determine many of its chemical properties - such as pH, cation exchange, lime requirement and P-buffer index. Some of the soil physical properties such as particle size, water-holding capacity and bulk density also depend on the distribution of soil components. Because the specific infrared signatures of these organic and mineral components are known, it is possible to predict many of the soil properties from single MIR spectra using PLS analysis. Infrared PLS analysis has been used since the 1980s for the prediction of sample properties from their spectra. Most of the early published work used the near infrared (NIR) spectral region for the analysis of cereal, meat and forages but the method is applicable to the prediction of y-data (properties) from any multidimensional x-data (spectra), including MIR spectra. Advantages of PLS are that it is rapid, can handle co-linear data, is a ‘full-spectrum’ method, and can provide useful qualitative information. PLS is a method with which the infrared spectra are reduced into latent variables, or loadings similar to principal components in PCA analysis, and scores (multipliers). These scores are then regressed with corresponding y-values, i.e. soil properties, and the PLS regressions saved as calibration models. A large number of soil properties, used to derive the calibration models, can then be predicted from the spectra of unknown samples. In principle, most soil calibrations require at least 100 samples per set, but current work suggests that calibration soil set sizes of at least 1,000 are required to account for the large variability within different soil types. Several large soil data sets from South Australia, Western Australia, New South Wales and Queensland have been used to calibrate the facility’s MIR spectrometer. The MIR Facility in AdelaideThe MIR facility at the CSIRO Land and Water Analytical Service Unit, Adelaide consists of a Perkin-Elmer Spectrum One rapid-scan Fourier-Transform mid-infrared (FTIR) spectrometer. Spectral range is from the NIR (7800cm-1) through to the MIR at 4000 to 450cm-1. Spectra are scanned for 1 minute at 8cm-1 resolution using a Perkin Elmer auto-focussing Diffuse Reflectance (DRIFT) sampling accessory. The MIR facility has also access to a field-portable FTIR spectrometer and has alternative sample introduction techniques including Attenuated Total Reflectance (ATR) and Photo-Acoustic Spectroscopy (PAS) for specialised research applications. Samples for DRIFT are usually reduced to a fine powder using a vibrating puck mill for fine grinding. The MIR service has access to a number of software options for PLS analysis, including a custom PLS prediction module designed for specific client applications. Price listPrices available on request, please contact Julie Smith for further information. Additional servicesAdvice (consulting)
Additional new calibration development
Research Support We can visually interpret variation in soils from peaks in their spectra without input from any lab data. From these peaks, we can attribute ‘soil-type’, general mineralogy and organic content. Site-specific maps can also be constructed using the relative variation of predicted soil properties (Table 1) mapped against the sample’s location. MIR Service Staff and Contact DetailsMs Julie Smith, Analytical
Chemistry Unit, MIR laboratory supervisor, (please contact for analyses
– see contact details below). Contact Details Analytical Enquiries Research Enquiries - Chief Research Scientist Dr Mike McLaughlin For further information contact:
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Copyright | Legal Notice and Disclaimer | Privacy Statement | Website Information Last updated: 28 January, 2011 |
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Light
energy in the mid infrared range 4000 to 500 cm-1 (2500 to
20,000nm) is focused onto the surface of the air-dry soil sample. Some
of this light is absorbed by the soil, but the rest is reflected back
into the spectrophotometer, detected and analysed. 