17 Agricultural Impacts on Hydrology and Water Quality in the Midwest II

Monday, 16 April 2018
1:30 PM - 5:30 PM
Room 250/252

SOIL AND STREAM SOLUTE FLUXES FROM AGRICULTURAL AND RESTORED PRAIRIE LAND USE

Paper number: 17-12
Program: Theme Sessions
Time: 5:05 PM – 5:25 PM

Authors

Abstract

Agricultural activities in the Midwestern United States have potentially altered geochemical fluxes within the critical zone (CZ) compared to native prairie systems that previously dominated the region. To quantify the impact of agricultural land use on soil and stream solute behavior, we are studying two watersheds in the region: Glacier Creek Preserve (GCP) in eastern Nebraska and the Intensively Managed Landscapes Critical Zone Observatory (IML-CZO) in eastern Iowa. Both watersheds were initially under agricultural land use for over 100 years, but part of each watershed was restored to prairie approximately 50 years ago. Soils at both sites formed in thick loess (>5 m) overlying glacial till with similar mean annual temperatures (10 °C) but slightly higher mean annual precipitation in Iowa (89 cm) compared to Nebraska (78 cm). At both sites, soil porewater, precipitation and stream water were collected every two to four weeks to measure anions, cations, oxygen isotopes, dissolved organic carbon and alkalinity. Both soil moisture content and electrical conductivity are consistently higher in the upper one meter of agricultural soils compared to prairie soils, implying slower drainage and higher solute concentrations in the agricultural soils. Soil porewater Ca and Mg concentrations are significantly higher in agricultural soils compared to restored prairie, but Ca and Mg concentrations in streams draining restored prairie are significantly higher than in streams draining agriculture. These observations lead to a conceptual model where deeply infiltrating water in restored prairie soils interacts with minerals present deeper in the soil before reaching the stream whereas in agricultural soils, water does not infiltrate as deeply and thus experiences more shallow flowpaths to the stream that do not dissolve deeper minerals. Thus, intense agricultural land use may alter soil function and solute transport to streams within this critical zone.

Geological Society of America Abstracts with Programs. Vol. 50, No. 4

doi: 10.1130/abs/2018NC-313060

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