Analysis of peat soil organic carbon, total nitrogen, soil water content and basal respiration: Is there a ‘best’ drying temperature?
Creators: name: Dettmann, Ullrich.
name: Kraft, Nicky Nancy
name: Rech, Raimund
name: Heidkamp, Arne
name: Tiemeyer, Bärbel
Publisher: name: Amsterdam [u.a.] : Elsevier Science
Year: 2021
Subjects: subject: Carbon dioxide flux
subject: Mineralisation
subject: Soil incubation experiment
subject: Soil moisture
subject: Soil organic matter
subject: Biogeochemistry
subject: Carbon dioxide
subject: Decomposition
subject: Drying
subject: Mineralogy
subject: Nitrogen
subject: Organic carbon
subject: Peat
subject: %moisture
subject: Amorphous samples
subject: Basal respiration
subject: Drying temperature
subject: Peat soils
subject: Soil organic carbon content
subject: Soil organic matters
subject: antimicrobial activity
subject: decomposition
subject: experimental study
subject: incubation
subject: peat soil
subject: respiration
subject: sedge
subject: soil nitrogen
subject: soil organic matter
subject: soil water
subject: thermal decomposition
subject: topsoil
subject: water content
subject: Sphagnum
subject: Dewey Decimal Classification::500 | Naturwissenschaften::550 | Geowissenschaften
subject: Dewey Decimal Classification::900 | Geschichte und Geografie::910 | Geografie, Reisen

description: Soil needs to be dried in order to determine water content, soil organic carbon content (SOC) and total nitrogen content (N). Water content is commonly measured using standard methods that involve drying temperatures of 105–110 °C. Recommended drying temperatures differ for the determination of SOC and N. However, at moderate drying temperatures, microbial activity might lead to organic matter mineralisation and nitrification, and thus to an underestimation of SOC and N. Furthermore, low drying temperatures might not dewater soils sufficiently to correctly determine water content or bulk density. Chemical processes such as thermal decomposition and volatilisation might occur at higher temperatures. This raises the question of whether the same sample can be used to determine water content, SOC and N. Further, the effect of drying, especially at different temperatures, on basal respiration of peat soils determined by incubation experiments is so far unknown. Effects of drying temperature might be especially severe for peat soils, which have high SOC and water contents. This study systematically evaluated the effect of different drying temperatures (20, 40, 60, 80 and 105 °C) on the determination of mass loss (proxy for water content), SOC and N over a wide range of 15 different peat soils comprising amorphous, Sphagnum and sedge peat substrate. The investigated peat soils had SOC contents ranging from approximately 16.8–52.5% with different degrees of decomposition. They were thus separated into two ‘peat groups’ (amorphous and weakly decomposed). In a subsequent investigation, an incubation experiment was carried out on a subset of five peat soils to investigate the pre-treatment effect of different drying temperatures on basal respiration. The results showed that amorphous samples should be dried at 105 °C to determine water content. The weakly decomposed peat soils in the study had reliable water contents for drying temperatures above 60 °C. For temperatures below 80 °C, the determined SOC and N were biased by residual water. This could be corrected for weakly decomposed samples, but for amorphous samples only for drying temperatures ≥60 °C. Thus, mineralisation of soil organic matter is likely to take place at lower drying temperatures which are not recommendable especially for amorphous peat prone to high mineralisation rates. This is supported by the results of the incubation experiment: The effect of peat type (amorphous topsoil vs. weakly decomposed subsoil) was greater than the effect of different drying temperatures, which nonetheless affected respiration rates. The differences between all five soils were consistent, irrespective of the drying temperature. Thus, incubation experiments might be possible using peat dried at moderate temperatures. © 2021 The Authors