Soil solution was collected from zero-tension lysimeters for 10 yr on two small central Appalachian watersheds in West Virginia, U.S.A. Ammonium sulfate fertilizer was applied to one catchment 3 times per year during each year. The other watershed was used as a reference to account for ambient baseline conditions. Ca and Mg concentrations collected below the A- and B-horizons of the treated watershed increased and then decreased over time as a result of the treatment. By contrast, Ca and Mg concentrations in the C-horizon continued to increase throughout the study period. The depletion in Ca and Mg that occurred in the upper levels apparently occurred due to charge pairing and leaching of those base cations with NO3 and SO4. The progressively greater amounts of Ca and Mg carried through the soil with these acid anions provided their continued increasing concentrations in the C-horizon. NO3 concentrations increased progressively with depth due to both the assimilation of NO3 by vegetation and microorganisms in the upper soil layers and leaching of NO3 into deeper soils by mesopore flow. NO3 became a more important ion over time with respect to pairing and leaching with base cations because its concentrations continued to increase in all soil layers, whereas SO4 became retained in all soil layers after several years of treatment, presumably induced by adsorption from increasing SO4 concentrations.
All Science Journal Classification (ASJC) codes
- Environmental Engineering
- Environmental Chemistry
- Ecological Modeling
- Water Science and Technology