ASTM D8438/D8438M-23

Standard Test Methods for Use of Hyperspectral Sensors for Soil Nutrient Analysis of Ground Based Samples

SIGNIFICANCE AND USE
5.1 Spectral analysis of soils for agricultural use is being used worldwide to obtain rapid data on soil nutrients. for the purpose of agricultural management including fertilizer application and other amendments such as pH adjustment, organic supplements, etc. Satellite, aerial, and ground-based sampling methods are being used. This test method applies to ground-based, terrestrial field applications where samples are taken from the ground, generally in the root zone. Use of these rapid remote sensing techniques allow for more detailed and economic data acquisition than older cumbersome sampling and wet chemistry testing methods used in the past by soil scientists for soil nutrient evaluations.  
5.2 This test method describes procedures for sampling and testing of field soils using diffuse reflectance spectrometry using handheld portable spectrometers measuring spectra in visible and near infrared (vis-NR) using dried sieved or wet samples. There is a worldwide effort to collect spectral databases of soils. The procedures specified here follow procedures as outlined in the United Nations Food and Agricultural Organization (FAO) primer on Vis-NIR and MIR spectroscopy of soils (1)3. Other organizations such as IEEE are actively working on additional guidance documents that will be incorporated in future revisions of this test method.  
5.2.1 This standard describes the procedures (Section 12) for using hyperspectral sensor data to measure moisture content as a percentage, pH, Organic Matter (OM) as a percentage, Cation Exchange Capacity (CEC) measured in 10 cmol c /kg could hold 10 cmol of Na + cations (with 1 unit of charge per cation) per kilogram of soil, but only 5 cmol Ca 2+ (2 units of charge per cation), as well as micro and macro nutrients in soils measured in PPM (parts per million)or a percentage, including, but not limited to nitrogen, phosphorous, potassium, boron, zinc, iron, sulfur, calcium, magnesium, and manganese.  
5.2.2 Research has shown that t...
SCOPE
1.1 This test method describes procedures for sampling and testing of soils obtained from ground-based samples using diffuse reflectance spectrometry using handheld portable spectrometers measuring spectra in visible and near infrared (vis-NR) and mid-infrared (MIR) range. The sensor can measure moisture content, PH, organic matter, Cation Exchange Capacity (CEC) as well as macro and micro elemental nutrients in parts per million (PPM) or percentage, including but not limited to nitrogen, phosphorous, potassium, zinc, iron, boron, sulfur, calcium, magnesium, and manganese.  
1.2 There are two methods that can be used to perform the test.  
1.2.1 Method A—The analysis is performed in the laboratory on the sample after the sample has been oven dried and sieved.  
1.2.2 Method B—The analysis is performed in the field on a moist sample after homogenization. After post-processing of multiple reflectance site data using methods A and B, the moisture content can be measured, and the spectral signature is normalized for moisture content.  
1.3 The limitation of this method is that the results of an individual test for elemental analysis would not be the same as exacting reference values from traditional wet chemical lab analysis used by soil scientists. Results of wet chemistry tests or tests from soil science libraries may be used to calibrate a specific site model comprised of many individual tests. Spectral data for organics has shown to be as accurate as conventional methods such as Test Methods D2974.  
1.4 For soil nutrient analysis the sample is not finely ground as in typical qualitative spectral analysis as outlined in standard Practice E1252. The spectrometer is checked periodically during testing using procedures in accordance with Guide E1866 performance testing.  
1.5 Moisture content is a preferred term in agricultural applications. For this standard, gravimetric water content may be measured in accordance wi...

General Information

• Status: Published
• Publication Date: 14-Feb-2023
• ICS: 13.080.30 - Biological properties of soils
• Technical Committee: D18 - Soil and Rock
• Drafting Committee: D18.01 - Surface and Subsurface Investigation

Relations

• Refers: ASTM D3740-23 - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-Nov-2023
• Refers: ASTM D2974-20e1 - Standard Test Methods for Determining the Water (Moisture) Content, Ash Content, and Organic Material of Peat and Other Organic Soils
• Effective Date: 15-Jan-2020
• Refers: ASTM D2974-20 - Standard Test Methods for Determining the Water (Moisture) Content, Ash Content, and Organic Material of Peat and Other Organic Soils
• Effective Date: 15-Jan-2020
• Refers: ASTM D3740-19 - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-Oct-2019
• Refers: ASTM D2216-19 - Standard Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass
• Effective Date: 01-Mar-2019
• Refers: ASTM D4643-17 - Standard Test Method for Determination of Water Content of Soil and Rock by Microwave Oven Heating
• Effective Date: 01-Feb-2017
• Refers: ASTM D4700-15 - Standard Guide for Soil Sampling from the Vadose Zone (Withdrawn 2024)
• Effective Date: 01-Feb-2015
• Refers: ASTM D2974-14 - Standard Test Methods for Moisture, Ash, and Organic Matter of Peat and Other Organic Soils
• Effective Date: 01-Nov-2014
• Refers: ASTM D653-14 - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Aug-2014
• Refers: ASTM E11-13 - Standard Specification for Woven Wire Test Sieve Cloth and Test Sieves
• Effective Date: 01-Oct-2013
• Refers: ASTM D2974-13 - Standard Test Methods for Moisture, Ash, and Organic Matter of Peat and Other Organic Soils
• Effective Date: 01-Jun-2013
• Refers: ASTM D3740-12a - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-May-2012
• Refers: ASTM D3740-12 - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-Mar-2012
• Refers: ASTM D653-11 - Standard Terminology Relating to Soil, Rock, and Contained Fluids
• Effective Date: 01-Sep-2011
• Refers: ASTM D3740-11 - Standard Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in Engineering Design and Construction
• Effective Date: 01-Sep-2011

Overview

ASTM D8438/D8438M-23 is an international standard providing procedures and recommendations for the use of hyperspectral sensors in the analysis of soil nutrients from ground-based samples. Developed by ASTM International, this standard addresses the growing need for cost-effective, rapid, and detailed soil nutrient information using advanced diffuse reflectance spectrometry in the visible, near-infrared (Vis-NIR), and mid-infrared (MIR) spectrum. This method supports advanced agricultural management, helping users make informed decisions about fertilizer application, organic supplementation, pH adjustment, and overall soil health.

Key Topics

• Purpose: Guides sampling and testing of soils using hyperspectral sensors for rapid soil nutrient analysis, facilitating efficient agricultural management.
• Test Methods: Two primary approaches:
  • Method A: Laboratory analysis of oven-dried, sieved soil samples.
  • Method B: Field analysis of moist, homogenized soil samples.
• Parameters Measured:
  • Moisture content
  • pH
  • Organic matter (OM)
  • Cation exchange capacity (CEC)
  • Macro and micronutrients: nitrogen, phosphorus, potassium, calcium, magnesium, manganese, sulfur, boron, zinc, and iron.
• Technological Advantages:
  • Non-destructive and rapid data collection.
  • High-density sampling using portable field spectrometers.
  • Normalization and calibration support using existing chemical soil analysis and global spectral databases.
• Limitations:
  • Results for certain nutrients may differ from wet chemistry reference lab values.
  • Calibration to local conditions using reference testing is recommended to ensure reliability.

Applications

• Agricultural Management: Hyperspectral soil analysis is revolutionizing how growers, agronomists, and land managers evaluate soil health, allowing for:
  • Precision fertilizer application based on real-time nutrient mapping.
  • Efficient amendment planning for optimal crop performance.
  • Large-scale nutrient databases to support regional and site-specific decision-making.
• Field and Laboratory Flexibility: Supports both lab-based and in-field measurements:
  • In-Field Sampling (Method B) enables immediate scanning and rapid site data collection, crucial for timely farming operations.
  • Lab Analysis (Method A) leverages controlled conditions to ensure consistency and calibrate field measurements.
• Regulatory and Research Use: Provides a validated framework that meets international standards, useful for compliance reporting, scientific research, and technology validation.

Related Standards

• ASTM D2216: Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass.
• ASTM D653: Terminology Relating to Soil, Rock, and Contained Fluids.
• ASTM D2974: Methods for Determining Water Content, Ash Content, and Organic Material of Peat and Other Organic Soils.
• ASTM E1252: Practice for General Techniques for Obtaining Infrared Spectra for Qualitative Analysis.
• ASTM E1866: Guide for Establishing Spectrophotometer Performance Tests.
• Referenced Guidance: United Nations FAO Vis-NIR and MIR spectroscopy of soils primer.
• Additional Guidelines: Local and regional agricultural regulations may specify minimum sample spacing and other requirements.

Conclusion

ASTM D8438/D8438M-23 delivers a robust and practical framework for integrating hyperspectral sensing into soil nutrient analysis, addressing the need for rapid, detailed, and economical data acquisition in agricultural and environmental management. Utilizing this standard supports more sustainable land use, precise nutrient management, and advances in digital soil mapping using remote sensing technologies.

Keywords: ASTM D8438, hyperspectral sensors, soil nutrient analysis, visible and near-infrared, agricultural management, field spectroscopy, soil testing, precision agriculture, soil sampling, nutrient mapping.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D8438/D8438M − 23
Standard Test Methods for
Use of Hyperspectral Sensors for Soil Nutrient Analysis of
Ground Based Samples
This standard is issued under the fixed designation D8438/D8438M; the number immediately following the designation indicates the
year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last
reapproval. A superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.5 Moisture content is a preferred term in agricultural
applications. For this standard, gravimetric water content may
1.1 This test method describes procedures for sampling and
be measured in accordance with Test Methods D2216 when
testing of soils obtained from ground-based samples using
drying samples and used to calibrate the site model, but the
diffuse reflectance spectrometry using handheld portable spec-
overall results of spectral analysis are more qualitative, and the
trometers measuring spectra in visible and near infrared
term Moisture Content is used in this standard.
(vis-NR) and mid-infrared (MIR) range. The sensor can
measure moisture content, PH, organic matter, Cation Ex- 1.6 Units—The values stated in either SI units or inch-
change Capacity (CEC) as well as macro and micro elemental pound units [given in brackets] are to be regarded separately as
nutrients in parts per million (PPM) or percentage, including standard. Wavelengths are stated only in nanometers, nm. The
but not limited to nitrogen, phosphorous, potassium, zinc, iron, values stated in each system may not be exact equivalents;
boron, sulfur, calcium, magnesium, and manganese. therefore, each system shall be used independently of the other.
Combining values from the two systems may result in noncon-
1.2 There are two methods that can be used to perform the
formance with the standard.
test.
1.2.1 Method A—The analysis is performed in the labora- 1.7 All observed and calculated values shall conform to the
tory on the sample after the sample has been oven dried and guidelines for significant digits and rounding established in
sieved. Practice D6026. The procedures used to specify how data is
1.2.2 Method B—The analysis is performed in the field on a collected, recorded or calculated in this standard are regarded
moist sample after homogenization. After post-processing of as the industry standard. In addition, they are representative of
multiple reflectance site data using methods A and B, the the significant digits that generally should be retained. The
moisture content can be measured, and the spectral signature is procedures used do not consider material variation, purpose for
normalized for moisture content. obtaining the data, special purpose studies, or any consider-
ations for the user’s objectives; and it is common practice to
1.3 The limitation of this method is that the results of an
increase or reduce significant digits of reported data to be
individual test for elemental analysis would not be the same as
commensurate with these considerations. It is beyond the scope
exacting reference values from traditional wet chemical lab
of this standard to consider significant digits used in analysis
analysis used by soil scientists. Results of wet chemistry tests
methods for engineering design.
or tests from soil science libraries may be used to calibrate a
1.7.1 Spectral data is acquired by electrical data acquisition
specific site model comprised of many individual tests. Spec-
systems and therefore numeric data is carried through record-
tral data for organics has shown to be as accurate as conven-
ing and into databases without rounding of numeric data.
tional methods such as Test Methods D2974.
1.8 This standard does not purport to address all of the
1.4 For soil nutrient analysis the sample is not finely ground
safety concerns, if any, associated with its use. It is the
as in typical qualitative spectral analysis as outlined in standard
responsibility of the user of this standard to establish appro-
Practice E1252. The spectrometer is checked periodically
priate safety, health, and environmental practices and deter-
during testing using procedures in accordance with Guide
mine the applicability of regulatory limitations prior to use.
E1866 performance testing.
1.9 This international standard was developed in accor-
dance with internationally recognized principles on standard-
This test method is under the jurisdiction of ASTM Committee D18 on Soil and
ization established in the Decision on Principles for the
Rock and is the direct responsibility of Subcommittee D18.01 on Surface and
Development of International Standards, Guides and Recom-
Subsurface Investigation.
mendations issued by the World Trade Organization Technical
Current edition approved Feb. 15, 2023. Published March 2023. DOI: 10.1520/
D8438_D8438M-23. Barriers to Trade (TBT) Committee.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D8438/D8438M − 23
2. Referenced Documents 4.1.2 Method B the samples are only homogenized via
2 mixing and stirring.
2.1 ASTM Standards:
D653 Terminology Relating to Soil, Rock, and Contained 4.2 The samples are then scanned with a hyperspectral
Fluids sensor to collect the spectral signature in the soil sample.
D2216 Test Methods for Laboratory Determination of Water
4.3 A reflectance and adsorption record for each test is
(Moisture) Content of Soil and Rock by Mass
obtained for each sample and all data are combined into a site
D2974 Test Methods for Determining the Water (Moisture)
database for post processing modeling calibration.
Content, Ash Content, and Organic Material of Peat and
Other Organic Soils
5. Significance and Use
D3740 Practice for Minimum Requirements for Agencies
5.1 Spectral analysis of soils for agricultural use is being
Engaged in Testing and/or Inspection of Soil and Rock as
used worldwide to obtain rapid data on soil nutrients. for the
Used in Engineering Design and Construction
purpose of agricultural management including fertilizer appli-
D4643 Test Method for Determination of Water Content of
cation and other amendments such as pH adjustment, organic
Soil and Rock by Microwave Oven Heating
supplements, etc. Satellite, aerial, and ground-based sampling
D4700 Guide for Soil Sampling from the Vadose Zone
methods are being used. This test method applies to ground-
D6026 Practice for Using Significant Digits and Data Re-
based, terrestrial field applications where samples are taken
cords in Geotechnical Data
from the ground, generally in the root zone. Use of these rapid
D6907 Practice for Sampling Soils and Contaminated Media
remote sensing techniques allow for more detailed and eco-
with Hand-Operated Bucket Augers
nomic data acquisition than older cumbersome sampling and
E11 Specification for Woven Wire Test Sieve Cloth and Test
wet chemistry testing methods used in the past by soil scientists
Sieves
for soil nutrient evaluations.
E1252 Practice for General Techniques for Obtaining Infra-
5.2 This test method describes procedures for sampling and
red Spectra for Qualitative Analysis
testing of field soils using diffuse reflectance spectrometry
E1866 Guide for Establishing Spectrophotometer Perfor-
using handheld portable spectrometers measuring spectra in
mance Tests
visible and near infrared (vis-NR) using dried sieved or wet
3. Terminology samples. There is a worldwide effort to collect spectral
databases of soils. The procedures specified here follow
3.1 Definitions—Terminology in accordance with Terminol-
procedures as outlined in the United Nations Food and Agri-
ogy D653 and shall be used where applicable.
cultural Organization (FAO) primer on Vis-NIR and MIR
3.2 Definitions of Terms Specific to This Standard: 3
spectroscopy of soils (1) . Other organizations such as IEEE
3.2.1 macro-nutrient, n—in agronomy, an element required
are actively working on additional guidance documents that
in large amounts for plant growth and development (for
will be incorporated in future revisions of this test method.
example, nitrogen, phosphorous and potassium).
5.2.1 This standard describes the procedures (Section 12)
3.2.2 micro-nutrient, n—in agronomy, an element required
for using hyperspectral sensor data to measure moisture
in smaller amounts for plant growth and development (for
content as a percentage, pH, Organic Matter (OM) as a
example, sulfur, calcium, magnesium, manganese, zinc,
percentage, Cation Exchange Capacity (CEC) measured in 10
copper, boron, iron, sodium).
cmol c /kg could hold 10 cmol of Na + cations (with 1 unit of
charge per cation) per kilogram of soil, but only 5 cmol Ca 2+
3.2.3 Power Spectral Density (PSD), n—in spectral
(2 units of charge per cation), as well as micro and macro
analysis, the energy variation that takes place within a vibra-
nutrients in soils measured in PPM (parts per million)or a
tional signal, measured as frequency per unit of mass.
percentage, including, but not limited to nitrogen,
3.3 Acronyms:
phosphorous, potassium, boron, zinc, iron, sulfur, calcium,
3.3.1 Vis-NIR—near infrared light spectrum from 350 to
magnesium, and manganese.
2500 nm.
5.2.2 Research has shown that the Vis-NIR data for OM
3.3.2 MIR—mid infrared light spectrum from 2500 to 4000
content is as accurate as other tests such as the burn off test in
nm.
Test Methods D2974(2). Analysis of natural moisture samples
using method B can provide faster testing and better estimates
4. Summary of Test Methods
of OM are normalization for moisture (3). Wet sampling allows
4.1 The test methods involve obtaining a sample that is
for many more samples to be rapidly scanned in the field and
homogenized to eliminate the effect of stratification.
therefore more samples and more detailed coverage of the site.
4.1.1 Method A the sample is air dried or dried in accor-
5.3 This standard does not address sensors that measure in
dance with Test Methods D2216 or Test Method D4643 then
the mid infrared range, MIR, are more expensive and there is
homogenized through sieving prior to scanning.
less spectral data available. MIR spectral analysis is performed
on dried samples that are finely grinded (4). MIR modeling
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on The boldface numbers in parentheses refer to a list of references at the end of
the ASTM website. this standard.
D8438/D8438M − 23
TABLE 1 Specifications for Vis-NIR Spectrometer
requires a high level of calibration against recognized labora-
tory procedures and physical properties. Wavelength Range 350-2500 nm
3 nm @ 700 nm
Resolution
5.4 Spectral data can differ from older reference tests
6 nm @ 1400/2100 nm
Scanning Time 100 milliseconds
typically based on wet chemistry methods such as pore fluid
Signal-to-Noise Ratio
extractions such as those outlined in soil survey manuals (5).
Visible Near Inferred 9000:1 @ 700 nm
These old methods require extensive labor costs and long
Short Wave Inferred 1 9000:1 @ 1400 nm
Short Wave Inferred 2 4000:1 @ 2100 nm
turnaround times. However, soil scientists are accumulating
Photometric Noise
large databases of spectral libraries which have been checked
-5
Visible Near Infrared 4.8 × 10 AU or
and calibrated with baseline chemical data. The soil survey
48 μAU@ 700 nm
-5
Short Wave Infrared 1 4.8 × 10 AU or
manual (5) also has early (2014) procedures for Vis-NIR
48 μAU@ 1400 nm
testing methods on dry specimens.
-4
Short Wave Infrared 2 1.1 × 10 AU or
110 μAU@ 2100 nm
5.5 The accuracy of the measurement is determined by the
Visible Near Infrared Detector (350-1000 nm) 512 element silicon
accuracy of the calibration of the baseline measurements that
array
are calibrated by chemical processing. On critical/new projects (1001-1800 nm) and
(1801-2500 nm)
the sampling plan may include samples for wet chemistry
Short Wave Infrared 1 and 2 Graded Index
testing to help calibrate the site model. The large amount of
Detectors InGaAs
Photodiode
data that is collected at a site is combined into a site-specific
TE Cooled
database which is subject to complex model training to
optimize the dataset. This standard will not provide detailed
guidance on modeling and the FAO document (1) provides a
NOTE 2—An ASD LabSpec Spectroradiometer is a commonly used
good overview of the current procedures for dataset modeling.
device. For MIR analysis A Bruker FTIR is a commonly used device (1,5).
Dataset modeling requires adjustments for texture, water
Lower cost spectrometers with limited wavelength ranges are available
content, and geology and generally is linked to other appropri-
but may not meet the specifications of Table 1 and may result in inaccurate
ate spectral libraries available from many sources (6). estimation of soil properties. Each spectrometer comes with its own
computer and data reduction programs and calibration models (7).
5.5.1 Horizon and Soil taxonomic order as auxiliary vari-
ables improve prediction accuracy of models. Regional, local,
6.2 White Reference Tile—Compressed Polytetrafluoroeth-
and past site-specific data, and taxonomic historic data base ylene (PTFE) White reference tile to baseline the sample
libraries may be used to help calibrate a site model.
measurement. The tile should be enclosed in a protective
container when not in use, and protective measures should be
NOTE 1—The quality of the result produced by this standard is
taken during cleaning to prevent personnel from direct expo-
dependent on the competence of the personnel performing it, and the
sure to Perflourinated compounds (PFAs).
suitability of the equipment and facilities used. Agencies that meet the
criteria of Practice D3740 are generally considered capable of competent
6.2.1 The reference panel should be large enough to cover
and objective testing/sampling/inspection/etc. Users of this standard are
the entire field of view of the contact probe. No exact
cautioned that compliance with Practice D3740 does not in itself assure
measurement can be stated since equipment may vary.
reliable results. Reliable results depend on many factors; Practice D3740
provides a means of evaluating some of those factors.
6.3 Wavelength Reference Calibration Puck or Tape—
Manufacturer provided reference spectra check standard.
6. Apparatus
10mm Mylar calibration sheet is used.
6.1 Hyperspectral Vis-NIR Sensor—Any spectral sensor that
6.4 A Light Source, which could be a 50 Watt integrated
meets the requirements of Table 1 can be used. There are a
light source or a lamp with a single-ended quartz halogen
variety of desktop systems that can meet these specifications
filament capsule 4.25V, 4.5-Watt Halogen. Preferred light
but a sensor with contact probe with a minimum field of view
source is Tungsten Quartz Halogen b/1500rs.
of 10 mm [0.4 in.] is recommended for field testing. The sensor
6.5 Nonporous Container and Nonporous Tool to stir and
houses and A/D converter, computer, lamp, and fiber optic
homogenize sample. Stainless steel bowl and mixing tool such
cable (Note 2).
as a spoon, pestle, or 2 mm hand sieve are recommended. to
6.1.1 The sensor must have a minimum operating range of
350 nm to 2500 nm. reduce crop residue, debris, and gravel from being included in
sample.
6.1.2 Analysis Software—The computer software shall al-
low acquired sequences to be archived and retrieved for
6.6 Lab or Hand Sieve—Specification E11 2mm (No. 10)
evaluation and allow real time display of the IR spectra
sieve.
signature. The software should allow viewing of the reflectance
6.7 Sample Bags or Containers to be Used for Method
signature for specified wavelengths (350-2500 nm). Additional
A—Paper bags, plastic jars, zip-top bags.
processing operations on each raw image sequence (for
example, averaging, subtraction, noise reduction derivatives) 6.8 Sample Container for Use in Method B to Scan the
may be performed to improve detectability of subsurface Sample—The tall walled container must hold the sample and
elements and nutrients. minimize exposure to outside light when scanning. White
6.1.3 Lab benchtop devices should be equipped with mount- HDPE plastic jars and other tall wall containers 50 to 150 mm
ing specimen holders, or pucks specifically designed for soil [2 to 6 in.] diameter, this should be a nonporous container to
analysis. These are typically borosilicate petri dishes. reduce contaminants similar to a bucket, cup, HDPE jars can
D8438/D8438M − 23
also be used. A muglight is a closed system which prevents 8.1.4.2 Preservation, transport, and processing samples for
external light from entering the field of view and reduces the dry sampling (Method A).
loss of light from the halogen lamp. It is important that external 8.1.4.3 Field testing of samples (Method B) including fre-
light is controlled during the scanning process to produce quency of reference check testing.
replicable results. 8.1.4.4 Delineation of samples for any validation reference
(wet chemistry, moisture, pH, etc.) testing based on quality
6.9 Soil Sampler Probe to extract soil core with a minimum
control requirements.
diameter of 2 cm [1 in.]. The most commonly used sampler is
8.1.4.5 Equipment reference check testing and cleaning
the hand operated soil step sample tube or hammered Veih-
requirements. Manufacturer’s operations manuals should be
meyer agricultural samplers (Guide D4700). Hand bucket
followed. Wet scanning will require regular cleaning of the
augers (
...