1st International Conference of Soil and Agriculture:
TOWARDS SOIL SUSTAINABILITY
11–13 June 2024 • Lublin–Nałęczów, Poland

https://doi.org/10.24326/ICSA1.1.02
Published online: 4 October 2024

Storage of persistent organic matter in gypsum soils under temperate climatic conditions – a contribution of the soil macro- and microstructure
Krystyna Ciarkowska¹*, Messias de Carvalho¹, Leszek Wojnar², Katarzyna Sołek-Podwika¹

¹ Soil Science and Agrophysics Department, University of Agriculture in Krakow, Aleja Mickiewicza 21, 31-120 Kraków, Poland
² Department of Applied Infomatics, University of Technology, Al. Jana Pawła II 37, 31-864 Kraków, Poland
* Corresponding author:

Abstract
Soils are an important carbon (C) sink, with about 70% of the terrestrial organic C accumulated in soil organic matter (SOM). For this reason, SOM is essential to the soil environment, sustaining ecosystem health and functions. In our work we compared SOM content and stability in gypsum and limestone derived soils of the same areas and under similar physiographic conditions. We hypothesised that soils derived from gypsum have a special ability to accumulate persistent organic matter, mainly resulting from the presence of gypsum, which acts through the macro- and microstructure stabilisation. In our work, we aimed at: (i) comparing SOM amounts and decomposition state together with SOM related properties in gypsum soils and limestone soils, (ii) checking to what degree physical properties related to macro- and microstructure affect the soil organic matter properties and stability and the carbon sequestration. Properties of the soil humus horizons were determined, including texture, available potassium and phosphorus, pH, amount of gypsum and calcite, enzyme activity. Moreover, we examined soil thin sections in order to determine their microstructures and degree of SOM transformation at the microscopic level and quantified the results using image analysis. The study was performed in various location of the Nida Basin, on soils derived from selenite-type gypsum rocks and on carbonate bedrock. Stocks of organic carbon accumulated in 0–20 cm depth were much higher in gypsum soils (9.7–10.1 kg/m²) than in limestone soils (5.0–6.4 kg/m²). Studied soils differed in SOM stabilisation, which was expressed by higher C/N ratios, lower aggregate water resistance index, lower dehydrogenase activity, and greater areas of undecomposed or slightly decomposed plant residues observed in limestone soils comparing to gypsum ones. SOM amounts were strongly affected by gypsum and calcite contents, dehydrogenase activity, porosity and microaggregation. Gypsum soils were characterised by a higher share of more stable and water resistant microaggregates than limestone soils in which macroaggregates prevailed. Gypsum as a parent material favoured SOM accumulation through its physical stabilization, by providing active Ca cations to protect the SOM together with silt and clay, and its biochemical stabilization, through high enzyme activity. Our results show that gypsum soils are important as a response to global warming through their ability to preserve SOM over the long term.

Keywords: organic matter storage, soil physical properties, thin sections

How to cite
Ciarkowska K., de Carvalho M., Wojnar L., Sołek-Podwika K., 2024. Storage of persistent organic matter in gypsum soils under temperate climatic conditions – a contribution of the soil macro- and microstructure. 1st International Conference of Soil and Agriculture: Towards Soil Sustainability. https://doi.org/10.24326/ICSA1.1.02