Browsing by Subject "iron reduction"

Anticipated climate change-related shifts in precipitation patterns in Finland may lead to increased off-season rainfall, potentially causing soil waterlogging. Agricultural soils have significant long-term organic carbon stabilization potential due to organic matter interactions with soil minerals, especially iron (hydr)oxides, which play a key role in stabilizing organic matter. However, iron's sensitivity to redox changes during waterlogging can trigger reduction reactions of iron that lead to iron (hydr)oxide dissolution, releasing the carbon stabilized by iron (hydr)oxides. Given the critical role of soil organic carbon in food production and climate change mitigation, it is imperative to expand our understanding of how altered climate conditions affect particularly soil carbon stabilized by soil minerals, across various soil types and depths. The aim of this work was to investigate interactive effects of climate change induced soil moisture changes and cover crop on concentration and fate of dissolved organic carbon (DOC), dissolved iron and total dissolved carbon (DC; including inorganic and organic C) in two different agricultural mineral soils. In greenhouse experiment, the undisturbed soil monoliths of clay and coarse soil were used to investigate if off-season waterlogging could release organic carbon stabilized by soil minerals. Soil monoliths were saturated with water and pore water samples were collected from three different depths prior, during and after water saturation to monitor changes in the concentrations of iron, DOC and DC. Soil moisture and redox potential (Eh) were also monitored throughout the experiment. The effect of soil type, depth and cover crop on DC as well as differences in concentrations with time were statistically tested using linear mixed effects model and Tukey comparison test. The results of this study showed that waterlogging did not lead to reduction of iron and dissolution of iron (hydr)oxides, and consequently, no organic carbon adsorbed on iron (hydr)oxides was released. The presence of a cover crop did not significantly affect concentration of DOC or iron (hydr)oxide dissolution. However, signs of root exudate mineralization were observed under the cover crop treatment in the topsoil. Clay soil exhibited greater DC concentrations compared to coarse soil. Coarse soil showed signs of downward DOC movement during drainage, while clay soil's mid (30 cm) and bottom (50 cm) layers remained less responsive to soil moisture and Eh changes due to its more compact structure. In the future studies it would be important to focus on improving our understanding of the vulnerability of stabilized organic carbon to changing redox conditions in natural soil systems.