Spodosols are important soil types throughout much of the citrus belt
in the south and east coast regions of Florida, The spodic horizon in
these soils may play a role in restricting the transport of contaminan
ts; hence, it could minimize the contamination of groundwater by agric
hemicals applied to soils. In this study, adsorption and leaching of n
itrate and bromide in soil samples taken from three horizons of a Spod
osol (Oldsmar sand; sandy silicious, hyperthermic Alfic Arenic Haplaqu
ods) were evaluated with batch equilibration and leaching column exper
iments, Adsorption of nitrate and bromide was negligible by the A (sur
face soil, 0-20 cm) and E (sand layer, 25-50 cm) horizon samples, The
spodic horizon (B-h, 55-70 cm), by comparison, retained a small amount
of nitrate and bromide. In a leaching column study, the quantity of n
itrate, applied on the surface of the soil column, recovered in 4.5 po
re volumes of leachate was lower by 15% when the soil sample from the
spodic horizon was used compared with using the surface or the sand ho
rizon samples. A 2-fold increase in rate of application of either nitr
ate or bromide had a negligible effect on the cumulative leaching of t
he ions in relation to the quantity applied.