Why Soil Spectroscopy? Keith D Shepherd
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Transcript of Why Soil Spectroscopy? Keith D Shepherd
Hands-on Soil Infrared Spectroscopy Training Course
Getting the best out of light11 – 15 November 2013
Why Soil Spectroscopy?
Keith D Shepherd
Surveillance Science• Measure frequency of problems and associated risk factors in populations
using statistical sampling designs & standardized measurement protocolsUNEP. 2012. Land Health Surveillance: An Evidence-Based Approach to Land Ecosystem Management. Illustrated with a Case Study in the West Africa Sahel. United Nations Environment Programme, Nairobi.http://www.unep.org/dewa/Portals/67/pdf/LHS_Report_lowres.pdf
Shepherd KD and Walsh MG (2007) Infrared spectroscopy—enabling an evidence-based diagnostic surveillance approach to agricultural and environmental management in developing countries. Journal of Near Infrared Spectroscopy 15: 1-19.
Simplicity of light
Wavelength unit converter.xls
Spectral shape relates to basic soil properties
• Mineral composition• Iron oxides• Organic matter• Water (hydration,
hygroscopic, free)• Carbonates• Soluble salts• Particle size distribution
Functional properties
•Soil mineralogy•nutrient quantity (stock) and intensity (strength of
retention by soil)•pH and buffering, variable charge•anion and cation exchange capacity•carbon saturation; protection•aggregate stability, dispersion/flocculation•resistance to erosion
•Soil organic matter•soil structure•aggregate stability, resistance to erosion; water
holding capacity•carbon storage and turnover•cation exchange capacity•nitrogen, organic P, sulphur supply
Soil function largely determined by soil mineralogy and soil organic matter
Origin of infrared spectral absorption features
Water vibrations movie
Carbon dioxide-vibrations movie
SpectraSchool - Royal Society of Chemistryhttp://www.rsc.org/
Soil IR fundamentals
1 = Fingerprint region e.g Si-O-Si stretching/bending2 = Double-bond region (e.g. C=O, C=C, C=N)3 = Triple bond (e.g. C≡C, C≡N)4 = X–H stretching (e.g. O–H stretching)NIR = Overtones; key features clay lattice and water OH; SOM affects overall shape
Field spectroscopy
Shepherd KD and Walsh MG. (2002) Development of reflectance spectral libraries for characterization of soil properties. Soil Science Society of America Journal 66:988-998.
Infrared spectroscopy Dispersive VNIR FT-NIR FT-MIR Robotic FT-MIR Portable
Handheld MIR ?Mobile phone cameras ?
Brown D, Shepherd KD, Walsh MG (2006). Global soil characterization using a VNIR diffuse reflectance library and boosted regression trees. Geoderma 132:273–290.
Shepherd KD and Walsh MG (2007) Infrared spectroscopy—enabling an evidence-based diagnostic surveillance approach to agricultural and environmental management in developing countries. Journal of Near Infrared Spectroscopy 15: 1-19.
Terhoeven-Urselmans T, Vagen T-G, Spaargaren O, Shepherd KD. 2010. Prediction of soil fertility properties from a globally distributed soil mid-infrared spectral library. Soil Sci. Soc. Am. J. 74:1792–1799
Sample preparation/presentation
Instrument protocols
Fourier Transform Spectrometer
Dispersive spectrometer
Reference analyses
Data & soil library management
Barcoding
Soil archiving system
1.2 km shelving to hold over 40 t of soil
CalibrationSoil organic carbon Spectral pretreatments
• Derivatives, smoothing
Data mining algorithms:• PLS +• Support Vector
Machines• Neural networks• Multivariate Adaptive
Regression Splines• Boosted Regression
Trees• Random Forests• Bayesian Additive
Regression Trees
Training Out-of-bag validation
Soil pH
R package soil.specSoil spectral file conversion, data exploration and regression functions
Spectral libraries
Inter-instrument calibration transfer
Robotoic high throughput MIR
• Submit batch of spectra online
• Uncertainties estimated for each sample
• Samples with large error submitted for reference analysis
• Calibration models improve as more samples submitted
• All subscribers benefit
Soil-Plant Spectral Diagnostics Lab
•500 visitors/yr again
•338 instruction
•13 PhD, 4 MSc training
Spectral Lab Network
•IAMM, Mozambique
•AfSIS, Sotuba, Mali
•AfSIS, Salien, Tanzania
•AfSIS, Chitedze, Malawi
•CNLS, Nairobi, Kenya
•ICRAF, Nairobi, Kenya
•CNRA, Abidjan, Cote D’Ivoire
•KARI, Nairobi, Kenya
•ICRAF, Yaounde, Cameroon
•Obafemi Awolowo University, Ibadan, Nigeria
•IAR, Zaria, Nigeria
•ATA, Addis Ababa, Ethiopia (+ 5 on order)
•IITA, Ibadan, Nigeria
•IITA, Yaounde, Cameroon
•ICRAF, Nairobi, Kenya
Planned
•Eggerton University, Kenya
•MoA, Liberia
•IER, Arusha, Tanzania
•FMARD, Nigeria
•NIFOR, Nigeria
•CNLS, Nairobi
•BLGG, Kenya (mobile labs)
Spectral fingerprintingTotal X-ray fluorescence spectroscopy
X-ray diffraction spectroscopy
Mineral Semi-quant (%)
Quartz
Albite
Microclin
e
Kaolinite
Hematite
Muscovit
e
Diopside
69.2
5.0
4.3
9.9
2.8
4.3
4.6
Infrared spectroscopy
Land Health Surveillance
Consistent field protocol
Soil spectroscopyCoupling with
remote sensingPrevalence, Risk factors, Digital mapping
Sentinel sites Randomized sampling schemes
✓60 primary sentinel sites➡ 9,600 sampling plots➡ 19,200 “standard” soil samples➡ ~ 38,000 soil spectra➡ 3,000 infiltration tests➡ ~ 1,000 Landsat scenes➡ ~ 16 TB of remote sensing data
to date
AfSIS
Spectral prediction performance
Main AfSIS workflow, products & services overview
Markus Walsh, August 2013
Ethiopia: current spatial coverage of new ground observations and measurements
Africa Soil Information Service
www.africasoils.net
Markus Walsh, August 2013
Probability topsoil pH < 5.5 ... very acid soils
prob(pH < 5.5)Africa Soil
Information Servicewww.africasoils.net
Markus Walsh
[N] ppm [P] ppm [K] ppm
[S] ppm [Ca] ppm [Mg] ppm
“Best” current topsoil macro-nutrient (N,P,K,S,Ca & Mg) concentration predictions
Africa Soil Information Service
www.africasoils.net
Markus Walsh
Living Standards Measurement StudyIntegrated Surveys on Agriculture
LSMS-IMS
Improve measurements of agricultural productivity through methodological validation and research
Responding to policy needs to provide data to understand the determinants of social sector outcomes.
Soil fertility monitoring componentTwo pilot countries
MTT-Finland FoodAfrica
Soil Micronutrients
Healthy soils
Healthy crops
Healthy livestock
Healthy people
Evidence-based micronutrient management
Land HealthSurveillance Out-scaling
Tibetan Plateau/ Mekong
Vital signs
Cocoa - CDIParklands Malawi
National surveillance systems
Regional Information Systems
Project baselines
Ethiosis
Rangelands E/W AfricaSLM Cameroon MICCA EAfrica
Global-Continental Monitoring Systems
Evergreen Ag / Horn of Africa
CRP pan-tropical sites
AfSIS
Future directions
• Centralized calibration service on-line
• Direct calibration of MIR to plant/soil response data
• Rural MIR labs providing low cost soil testing for smallholder farmers
• Complementarity of IR, TXRF, XRD, Handheld XRF
• Decision cases