HR: 0800h
AN: H51C-0653    [Abstracts]
TI: Nutrient Retention by Spodosols in an Impacted Isolated Wetland
AU: * Bhadha, J H
EM: jango@ufl.edu
AF: University of Florida, Soil & Water Science, 2169-McCarty Hall, Gainesville, Fl 32611, United States
AU: Jawitz, J W
EM: jawitz@ufl.edu
AF: University of Florida, Soil & Water Science, 2169-McCarty Hall, Gainesville, Fl 32611, United States
AB: Agricultural soils within the Lake Okeechobee drainage basin can pose a nutrient management challenge because of their low nutrient retention capacity and hydrological setting. While hydrological restoration of isolated wetlands within the hydroscape may mitigate some phosphorus (P) loss from pastures, P retention mechanisms within these wetlands are difficult to control, and depend primarily on vegetation, antecedent soil conditions, and climate. The objective of this research was to: (i) Characterize soil properties responsible for nutrient retention such as, texture, bulk density, particle density, porosity, soil organic matter (OM) and total P (TP) concentrations, and distinct hydric soil indicators; and (ii) Use steady-state diagenetic equations to describe the effect of physical and biological processes using a low authigenic phosphate (PO₄) precipitation rate on measured soil pore water profiles. Results indicate that the spodosols exhibit a modified A-horizon within the upper few centimeters, a sandy illuviated E-horizon, a loamy Bt-horizon interspersed with Fe-Al redoximorphic features, a Bh-horizon with slightly higher soil TP concentrations, contained over a high density-low conductivity argillic clay horizon, and at least three distinct hydric soil indicators observed within the top 15 cm. An inverse relationship between porosity (17-50 %) and bulk density (0.8-2.2 g.cm^-3) was attributed to physical stresses such as tillage and compaction. Based on the strong correlation between soil OM and TP we conclude that a large fraction of the soil P is organic, and not derived from inorganic agricultural amendments. However, the low sorption capacity of P by spodosols can pose a threat to downstream aquatic systems through ground water pathways, restricted only by the presence of semi-confining clayey horizons (below 120 cm depth) that may behave as preferential flow paths, and possibly retaining some of the P from solution onto its reaction sites. Lastly, pore water PO₄ concentrations could not be explained using steady-state diagenetic equations in the upper 30 cm, however, below 30 cm pore water PO₄ concentrations could be a result of antecedent soil conditions, and a slow precipitation rate of phosphatic minerals.
DE: 0486 Soils/pedology (1865)
DE: 1865 Soils (0486)
DE: 1890 Wetlands (0497)
SC: Hydrology [H]
MN: 2007 Fall Meeting