The Impact of Profile Genesis and Land Use of Histosol on Its Organic Substance Stability and Humic Acid Quality at the Molecular Level

Abstract

This study is designed to evaluate soil organic matter (SOM) quality indicators: molecular indicators of dissolved organic matter (DOM) and hydrophobicity of humic acid (HA), distribution of quantity in humified and labile fractions of histosols during renaturalization. The aim is to determine the differences in the qualitative composition of humic acids at the molecular level, which are decided by the previous tillage and genesis, and to evaluate the impact of anthropogenization on the peat soil according to hydrophobicity, as well as to estimate the impact of soil genesis and removing peat layer. Soil samples were taken from the three Sapric Histosol (according to WRB2022) profiles and the 0–30 cm layer in three field replicates (Lithuania, Radviliskis mun.). Our study suggested that in the differently managed drained Sapric Histosol under renaturalization, the most significant changes occurred in the topsoil layer (0–30 cm), in which an increase in the content of SOM particles 106–2 µm in size. It is expedient to grow perennial grasses and legumes to maintain the soil organic carbon stability mobile humic acids to mobile fulvic acids ratio (MHA:MFA 0.83 to 0.86). An evaluation of the quality of HA (E4:E6) revealed their highest maturity in the unfertilized perennial grasses (3.88) and crop rotation (3.87) with grasses. The highest concentrations of hydrophilic groups (ratio of the C=O to O-H) were found in Sapric Histosol under deciduous hardwood forest (12.33). The lowest hydrophilicity (9.25 and 9.36) was of the crop rotation Sapric Histosol with removed peat layer. The most sustainable use of drained Sapric Histosol in the context of the sustainability and quality of its humus substances should be associated with the formation of perennial grass and clover grassland and the cultivation of deciduous hardwood. Therefore, the horizon forms on the top part of the profile, which protects deeper Histosolic material layers from its mineralization.

Evaluation of Topsoil Carbon Content and Quality in a Peatland and Reforested Soil after 50 Years of Soil Restoration in the Sierra de Guadarrama National Park (Spain)

“…On the one hand, there is the loss of fertile soils, both natural and cultivated, along with the associated environmental and socio-economic problems that this fact generates, and, on the other hand, there is the emission of CO 2 to the atmosphere due to the degradation of the soil organic matter (SOM). These facts have increased interest in this problem, and some researchers have focused on SOM stabilization pathways, organomineral interactions, and chemical stability [6][7][8][9], while others have focused on evaluating the impact of different soil management practices on SOM content and quality [10][11][12][13]. Finally, all of them have the common objective of shedding light on stabilization pathways to prevent the loss of this carbon and to better understand the transformation mechanisms.…”

“…This fraction may provide information about the humification processes reflected in its chemical structure [10,11]. The study of the chemical composition of SOM and its fractions is important to understand its degree of transformation and stability, for which several techniques have been developed [11,12]. Among all of the analytical techniques, there are two that have given us a good idea about the degree of transformation of organic carbon: UV-visible spectroscopy and infrared (IR) spectroscopy.…”