Skip to main content

Evaluation of a microplate spectrophotometer for soil organic carbon determination in south-central Idaho

Bierer, A.M. and Leytem, A.B. and Dungan, R.S. and Rogers, C.W. (2020) Evaluation of a microplate spectrophotometer for soil organic carbon determination in south-central Idaho. Soil Science Society of America Journal. 3 September 2020. pp. 1-14. Available:

[img] Text

Download (1MB)


Soil organic carbon (SOC) is traditionally measured through dry combustion of soil but is inaccurate in soils recently limed or containing carbonates. Soils of south central Idaho contain carbonates therefore 3 alternative methods are typically used. Walkley-Black titration (WBTIT) has an extensive history but generates a large volume of hazardous waste for each sample analyzed. Low temperature loss on ignition (LOI360°C) may be utilized but requires frequent sample manipulation and is therefore prone to human error. A pressure calcimeter (Pcal) may be used, however the sample container may leak leading to inaccurate results. Therefore, a new method of SOC determination (WBSPEC) utilizing a microplate spectrophotometer was compared to LOI360°C, Pcal, and WBTIT in 75 south central Idaho soils and 10 standard soils. First, it was confirmed that soils of south central Idaho contain carbonates leading to inaccurate SOC determination by dry combustion. During the alternative method comparison, the WBSPEC method reduced waste production over the traditional WBTIT method by 89% while reducing sample handling over LOI360°C. The LOI360°C and WBTIT methods were most similar, however, the WBSPEC method performed adequately; the Pcal method often overestimated SOC compared to each other method. As the low SOC soils of south central Idaho were of particular interest, the methods were compared a second time on low SOC (<13.11 g kg-1) soils. Here, SOC determination was challenging however the WBSPEC method followed other methods well. It was determined that WBSPEC allows for accurate SOC determination in low SOC soils containing carbonates while reducing hazardous waste production and sample handling.

Item Type: Article
NWISRL Publication Number: 1699
Subjects: Soil > Chemistry
Depositing User: Users 6 not found.
Date Deposited: 11 Mar 2021 17:11
Last Modified: 11 Mar 2021 17:11
Item ID: 1737