Autor:innen:
Lucas Kohl | Justus Liebig Universität Gießen | Germany
Clarissa Duschek | Georg August University Göttingen
Atilla Öztürk | Technische Universität Berlin
Dr. Karolina Golicz
Eva-Maria L. Minarsch
Dr. Wiebke Niether
Dr. Christian Ahl | Georg August University Göttingen
Prof. Dr. Andreas Gattinger | Justus Liebig Universität Gießen
Increasing soil organic carbon (SOC) content leads to higher soil quality levels and resilience against extreme weather events caused by climate change. Beside this, it can also help to mitigate climate change by sequestering carbon dioxide in form of organic carbon in soil, e.g. in agricultural fields. Practical and reliable quantification of SOC is up to date lacking, but mandatory to enhance broad applicability in terms of carbon farming. Common laboratory-based methods for precise quantification are cost-, and labour-intensive and can be obliged to high risks of errors during the long procedure line. Sensor-based in-field methods to quantify SOC could be a solution to avoid these problems. However, the quantification quality has not been independently acknowledged yet.
The aim of this study was to compare different methods to quantify SOC, including one in-field method and three standard laboratory-based methods. The latter comprised two different laboratory total organic carbon (TOC) methods and one laboratory total carbon (TC) method analysed in two different laboratories. The in-field method was a direct, non-invasive, sensor-based TOC analysis. Soil samples from nine different agricultural sites in Hesse and Lower Saxony, Germany, were analysed within this study. Furthermore, soil physical (bulk density, rock fragment, soil texture) and chemical (pH, P2O5, K2O and Mg) parameters were measured. The equivalence of the different SOC methods was validated by four different statistical criterions: limits of agreement, accuracy, precision, and agreement in measurement of data pairs obtained from the same subject. Pearson correlation was used to correlate the calculated differences of the different SOC methods with the soil parameters.
None of the applied method comparisons met all statistical criteria. However, comparison of the two TOC laboratory methods showed the strongest equivalence. An influence of pH on the difference of the standard laboratory method TOC and in-field method was detected by Pearson correlation. This indicates the need to delimitate in-field quantification to certain pH-levels. Overall, the application of the portable in-field method has potential for future SOC monitoring.