The Composition of Dissolved Organic Matter in Arable Lands: Does Soil Management Practice Matter?

Abstract

Dissolved organic matter (DOM) is a key soil quality property, indicative of the organic matter stored in the soil, which may also be a function of temporal variation. This study examines whether DOM is a robust property of the soil, controlling fertility, or if it may change with time. Altogether eight sets of soil samples were collected in 2018 and 2019 from the cultivated topsoil (0–10 cm) of cropland and from a nearby grassland near Martonvásár, Hungary. The study sites were characterized by Chernozem soil and were part of a long-term experimental project comparing the effects of manure application and fertilization to the control under maize and wheat monocultures. DOM was extracted from the samples with distilled water. The dissolved organic carbon (DOC), total dissolved nitrogen (DN), biological index (BIX), fluorescence index (FI), humification index (HIX), carbon nitrogen (C/N) ratio and specific ultraviolet absorbance at 254 nm (SUVA254) index were studied in the arable soils, and the results showed that all the DOM samples were humified, suggesting relevant microbiological contributions to the decomposition of OM and its conversion into more complex molecules (FI = 1.2–1.5, BIX = ~0.5, and HIX = ~0.9). Temporal variations were detected only for the permanent grassland where higher DOM concentration was found in spring. This increased DOM content mainly originated from humified, solid phase associated, recalcitrant OM. In contrast, there were no differences among fertilization treatments and sampling dates under cropfield conditions. Moreover, climatic conditions were not proven as a general ruler of DOM properties. Therefore, momentary DOM alone is not necessarily the direct property of soil organic matter under cropfield conditions. The application of this measure needs further details of sampling conditions to achieve adequate comparability.

Micro-biological degradation and transformation of dissolved organic matter following continuous cropping of tobacco

“…The plant rhizosphere soil environment is changeable, and longterm monoculture significantly disturbs many soil factors, e.g., nutrients and microbial communities (Chen et al, 2020). Dissolved organic matter (DOM), which can directly reflect organic matter (OM) stored in the soil, is a key soil quality property (Al-Graiti et al, 2022). DOM is defined as a ubiquitous mixture of organic compounds in terrestrial ecosystems, the mobility of which affects the circulation and distribution of both carbon and nutrients in soil (Fox et al, 2018;Hu et al, 2021).…”

“…Additionally, various researchers have shown that the aliphatic/proteins DOM has poor stability and are decomposed faster, while lignin/CRAM-like DOM is degraded into aromatic compounds with lower H/C (Kaiser and Kalbitz, 2012). In a naturally stable ecosystem, such as a native forest, DOM is generally composed of a specific soil organic matter (SOM) content and composition (Al-Graiti et al, 2022). However, due to the use of frequent tillage, a considerable part of SOM is lost, resulting in the biodegradation and rapid mineralization of SOM (Virginia et al, 2022).…”