Transformation of Organic Soils Due to Artificial Drainage and Agricultural Use in Poland

Abstract

Organic soils that had been drained in order to obtain fertile agricultural land underwent changes leading to the formation of mursh (also known as moorsh). The mursh-forming process is a generic soil process that occurs in drained (artificially or naturally) organic soils, and leads to the changes in soil morphology, soil physical properties (including water retention capability), physicochemical properties, and chemical and biological properties. The aim of the paper is to present scientific knowledge on mursh soils, especially those that are not available to the wider audience. We firstly reviewed scientific literature on the mursh (moorsh) forming process of drained organic soils used for agriculture. We described the specific character of organic soils, differences between mursh and peat, the origin of the mursh-forming process, and the classification of organic soils (Histosols). Additionally, we described the changes in organic matter, such as the loss of soil carbon, increase of availability of plant nutrients, and leaching of biogens to groundwater. We revealed that the mineral matter in organic soils can be an indicator for distinguishing various types of murshes. We have highlighted the current gaps in the research that need to be filled in. The mursh-forming process is inherently related to the mineralization of soil organic matter and leads to a reduction of organic carbon in soil. Mursh has many unfavorable properties with regards to agriculture and environmental management. These properties are mainly related to decreased water storage capacity, which significantly limits the hydrological function of organic soils. The use of drained organic soils is a trade-off between environmental quality and agricultural production.

Distribution of Mercury in Drained Peatlands as the Effect of Secondary Transformation of Soil Organic Matter

“…It may be the effect of considerable biological activity as well as the inflow of fresh organic matter from the existing vegetation. Hence, we confirmed the association reported in the literature that peatland soil drainage and intensification of the process of secondary transformations enhance organic matter humification and increase the share of humic substances in the soil matter [52,54,68,84]. An increase in the ash content of the study soils, and a simultaneous decline in TC content and increase in bulk density, was accompanied by significantly lower values of the TC/TN ratio (Table 6).…”

“…The M1 and M2 horizons were found to form a uniform group compared to the layers below them; the group was characterised by a significantly higher ash content, greater density (higher ρ a values), lower TC content and lower values of the TC/TN ratio. The obtained variation in the properties of the examined profiles is typical of drained organic soils of fern peatlands [52,54,55,67,68,70]. Processes of rapid organic matter decomposition contributed to a significant decline in organic matter content and nitrogen accumulation and, as a consequence, to lowering the values of the TC/TN ratio.…”

“…Strong binding of mercury in soils is due to its high chemical affinity for organic matter [4,6,18,[49][50][51]. Peatland drainage (very frequent in case of utilisation of organic soils) stimulates aerobic organic matter decomposition, production of dissolved organic matter (DOM) and humic substances (HS) [52][53][54][55]. Dissolved organic matter affects mercury speciation, mobility and toxicity in the environment [8,9,19,50,[56][57][58][59].…”

“…Fluctuating groundwater levels result in, e.g., thermal changes in the soil and in pH values; they also affect vegetation cover [62][63][64]. These factors may affect mercury accumulation in soil [1,4,7,38,47,49,57,65,66]; (v) Peatland drainage and agricultural utilisation result in increased soil trophicity which is followed by the enhanced microbiological activity of the soil [54,67,68]. In the study by Wang et al [66], net production of methylmercury was positively correlated with the trophic requirements of vegetation and an increased availability of electron acceptors and donors for mercury-methylating microorganisms.…”

“…Peatland drainage for farming purposes is a major cause of fen peatland degradation in the temperate climate [69]. Peat degradation is followed by the formation of a murshic horizons which has an aggregate structure and a greater quantity of humic substances [52,54,68,70]. The process of peatland drainage is progressing due to climatic change which contributes to a negative water balance that is unfavourable for peatland development [71,72].…”