ASTM D8438/D8438M-23
(Test Method)Standard Test Methods for Use of Hyperspectral Sensors for Soil Nutrient Analysis of Ground Based Samples
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
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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
1
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-
1
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
...
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