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Standard Test Methods for Use of Hyperspectral Sensors for Soil Nutrient Analysis of Ground Based SamplesPřeložit název
NORMA vydána dne 15.2.2023
Označení normy: ASTM D8438/D8438M-23
Datum vydání normy: 15.2.2023
Kód zboží: NS-1136288
Počet stran: 7
Přibližná hmotnost: 21 g (0.05 liber)
Země: Americká technická norma
Kategorie: Technické normy ASTM
agricultural management, agriculture, hyperspectral, hyperspectral sensor, nutrient analysis, soil nutrients, soil testing,
|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 (). 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 ) 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 the Vis-NIR data for OM content is as accurate as other tests such as the burn off test in Test Methods 5.3?This standard does not address sensors that measure in the mid infrared range, MIR, are more expensive and there is less spectral data available. MIR spectral analysis is performed on dried samples that are finely grinded 5.4?Spectral data can differ from older reference tests typically based on wet chemistry methods such as pore fluid extractions such as those outlined in soil survey manuals 5.5?The accuracy of the measurement is determined by the accuracy of the calibration of the baseline measurements that are calibrated by chemical processing. On critical/new projects the sampling plan may include samples for wet chemistry testing to help calibrate the site model. The large amount of data that is collected at a site is combined into a site-specific 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 5.5.1?Horizon and Soil taxonomic order as auxiliary variables improve prediction accuracy of models. Regional, local, and past site-specific data, and taxonomic historic data base libraries may be used to help calibrate a site model.
Note 1:?The quality of the result produced by this standard is dependent on the competence of the personnel performing it, and the suitability of the equipment and facilities used. Agencies that meet the criteria of Practice are generally considered capable of competent and objective testing/sampling/inspection/etc. Users of this standard are cautioned that compliance with Practice does not in itself assure reliable results. Reliable results depend on many factors; Practice provides a means of evaluating some of those factors.
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 AThe analysis is performed in the laboratory on the sample after the sample has been oven dried and sieved.
1.2.2?Method BThe 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 .
1.4?For soil nutrient analysis the sample is not finely ground as in typical qualitative spectral analysis as outlined in standard Practice . The spectrometer is checked periodically during testing using procedures in accordance with Guide performance testing.
1.5?Moisture content is a preferred term in agricultural applications. For this standard, gravimetric water content may be measured in accordance with Test Methods when drying samples and used to calibrate the site model, but the overall results of spectral analysis are more qualitative, and the term Moisture Content is used in this standard.
1.6?UnitsThe values stated in either SI units or inch-pound units [given in brackets] are to be regarded separately as standard. Wavelengths are stated only in nanometers, nm. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with the standard.
1.7?All observed and calculated values shall conform to the guidelines for significant digits and rounding established in Practice . The procedures used to specify how data is collected, recorded or calculated in this standard are regarded as the industry standard. In addition, they are representative of the significant digits that generally should be retained. The procedures used do not consider material variation, purpose for obtaining the data, special purpose studies, or any considerations for the users objectives; and it is common practice to increase or reduce significant digits of reported data to be commensurate with these considerations. It is beyond the scope of this standard to consider significant digits used in analysis methods for engineering design.
1.7.1?Spectral data is acquired by electrical data acquisition systems and therefore numeric data is carried through recording and into databases without rounding of numeric data.
1.8?This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.9?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.
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