Carbon and nitrogen contents of soil organic matter fractions, soil organic carbon, total soil nitrogen, and soil organic matter of 100 topsoil samples from the UKCEH Countryside Survey, Great Britain, 2019-2020

Archived Countryside survey topsoil samples (0-15 cm) were used. These were sieved (2 mm) and airdried prior to archiving.
Thermo-Gravimetric Analysis was performed in four steps using a LECO TGA701. 10 g of samples were heated from 25oC to 105oC (kept constant for 3 h) to determine the hygroscopic moisture. The mass loss between 105oC and 375oC (kept constant for 15.75 h) was used to calculate the soil organic matter content (SOM), the mass loss between 650oC and 100oC gives information on calcium carbonate content of the soils.
Soil organic matter fractions were separated via density fractionation using sodium polytungstene at 1.8 g cm-3). In the first step, the free light fraction (LF-fraction) was separated using 2.5 g archived soil. The pellet was re-suspended, and the occluded fraction was separated and discarded. The residual material was associated with the mineral associated organic matter fraction (MAOM fraction) after re-suspension and cleaning. Two internal standards were used in each batch as well as 10% of replicated samples to account for accuracy and precision.
Carbon and nitrogen contents were measured on a subsample of archived soil, and the LF and MAOM fractions using an Elementar Vario-Elemental analyser (Elementaranalysensysteme GmbH, Hanau, Germany). The UKAS accredited method SOP3102 was used.
Carbon and nitrogen mass fractions were calculated for the LF and MAOM fractions, and the soil. Mass fractions of the occluded fraction (OF) and the particulate organic matter fraction (POM) were calculated using the mass balance equation.
Total soil carbon and MAOM-C are corrected for calcite-C content; LF, OF and POM fractions are not corrected for calcite content because no minerals are expected to be present in organic matter.
LF, MAOM, total soil, and SOC (total soil carbon minus calciate-carbon) were corrected for hygroscopic water content. The OF and POM fractions are automatically corrected for hygroscopic water as they are calculated from corrected masses.

Related datasets

Topsoil physico-chemical properties from the UKCEH Countryside Survey, Great Britain, 2018-2019

Topsoil physico-chemical properties from the UKCEH Countryside Survey, Great Britain, 2020, v2

This dataset is included in the following collections

Countryside Survey