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Proposal

Soil water dynamics influence vegetation health, soil geochemical reactions, and stream chemistry. Water dynamics can be controlled by soil type and land management. It is important to understand water movement due to its influence on soil weathering, microbial activity, and nutrient transport. Water movement can be investigated using water stable isotope variability as a tracer. The purpose of this ongoing study was to analyze stable isotopes and dissolved ions in prairie and agricultural land management sites in Nebraska and Illinois. Prairies typically contain deep-rooted grasses, while agricultural lands contain shallow-rooted row crops. Root depth is considered a major control on rainwater infiltration depths. Soil type and structure also influence infiltration rates, with water moving more easily through coarse sand than fine-textured clays. We hypothesize that soil type influences water residence time, which leads to differences in stable isotope contents. Soil porewater at both Illinois sites showed reduced isotope variability compared to sites in Nebraska, suggesting more mixing of rain events and longer residence times of water in the soil. Through major ion analyses, the Illinois sites were found to have higher electrical conductivities at depth compared to those of the Nebraska sites, likely due to the clay content in the soils increasing the residence time of water, resulting in increased accumulation of mineral weathering. Our results show that soil properties like clay content and vegetation type affect water movement through different soils.

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