ISO 18386:2025

International
Standard
ISO 18386
First edition
Soil quality — Screening method for
2025-06
soil temperature — Measurement
by infrared (IR) thermometer
Qualité du sol — Méthode de criblage pour la température du sol
— Mesure par thermomètre infrarouge (IR)
Reference number
© ISO 2025
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ii
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle and application . . 1
4.1 Fundamentals .1
4.2 IR detection principle .2
4.3 Typical original application of IR thermometers .2
4.4 Diversion of IR thermometers to soil temperature measurement .2
5 Apparatus . 3
6 Procedure . 3
6.1 General .3
6.2 Drilling a hole.3
6.3 IR detection .3
6.3.1 General .3
6.3.2 Close-to-a-spot measurement . . .4
6.3.3 Remote measurement .4
7 Quality assurance and quality control . 4
8 Test report . 4
Bibliography . 5

iii
Foreword
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This document was prepared by Technical Committee ISO/TC 190, Soil quality, Subcommittee SC 3, Chemical
and physical characterization.
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iv
Introduction
Soil temperature gives useful information in the engineering and industrial fields, especially geology,
geotechnics, biology and agriculture. In recent years, climate change issues have been discussed globally,
including greenhouse gas emissions from soil. Microbial decomposition of organic matter contributes to
greenhouse gas emissions from soils, with the activity of the microbes and hence the rate or flux of these
emissions dependent on soil temperature. Hence the temperature of the soil can be an indirect indicator
of its risk of greenhouse gas emissions. Soil temperature directly affects the growth of plants. Optimum
temperatures or temperature ranges exist for plant germination, growth and ultimately yield.
The guidance document for measurement of soil temperature (ISO 4974) describes two approaches,
depending on the purpose of the investigation and the accuracy required. Conventional measurement is
applied where greater accuracy is needed, whereas quick measurements can be made (e.g. using an infrared
(IR) thermometer) where accuracy is not as critical, thus allowing to improve measurement efficiency (e.g.
measurement time per spot) in exchange for accuracy.
This document describes the principle of quick measurement for soil temperature applying infrared (IR)
detection, which is briefly introduced (without the measurement procedure descriptions) in ISO 4974 as one
of the soil temperature measurement methods. ISO 4974 contains general discussions about temperature
and its measurement principles, including what soil temperature is, why it is measured, by what kinds of
principles it can be measured and how measurement methods should be appropriately selected depending
on given soil temperature measurement purposes. This document describes the details of a specific soil
temperature measurement procedure using an IR thermometer and explains the measurement principle.
This method is positioned as one of the screening methods which have been developed under the concept
designated in ISO 12404, which is a general guidance document of screening methods.

v
International Standard ISO 18386:2025(en)
Soil quality — Screening method for soil temperature —
Measurement by infrared (IR) thermometer
1 Scope
This document specifies a method for quick measurement of soil temperature using an infrared (IR)
thermometer.
The method is applicable to a variety of technical fields, including geology, geotechnics, biology and
agricultural sciences, as well as climate change studies and metrological investigation.
NOTE The method designated in this document is recognized as a quick measurement in ISO 4974 and meets the
definition of screening method as designated in ISO 12404:2021, 3.2.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
soil temperature
temperature measured at a targeted spot in the soil or at the soil surface
Note 1 to entry: The temperature at a spot in the ground shallower than 300 mm is affected by the atmospheric
temperature. When mea
...