Organic soils subside when they are drained continuously, primarily
because of aerobic microbial activity. The purpose of this study was to
determine the organic matter oxidation potential of an organic soil that
is the result of intermittent flooding and draining in combination with
different water table depths, some suitable for the culture of sugarcane.
A 2-year outdoor study was conducted with lysimeters filled with a Pahokee
muck soil (Euic, hyperthermic Lithic Haplosaprist) and planted to
sugarcane (interspecific hybrids of Saccharum spp.). Treatments were
flooding for 7 days, followed by drainage for 14 days to 16-, 33-, or 50-
cm water table levels below the soil surface. A continuous drain treat- ment to a 50-cm water table was included as a control. Soils were sampled
during four flood/drain cycles in both years. Oxidation of 14C
(carboxyl)-benzoate applied to soil was used to estimate oxidation po- tential. In the continuously drained treatment, oxidation potential remained
constant at 457 nmol CO2 kg!1 soil h!1. In the treatments of
flood followed by drainage to 33- and 50-cm depths, soil organic matter
oxidation potential increased immediately upon drainage and reached
close to maximum activity (384 and 473 nmol CO2 kg!1 soil h!1, respectively)
in 3 to 7 days. Oxidation potential in the 16-cm water table
declined from 339 to 289 nmol CO2 kg!1 soil h!1 during the drainage cycle,
possibly due to inhibitory influences in the sugarcane rhizosphere on
microbial activity. Histosols may not need to be submerged continuously
to reduce oxidation potential substantially. Two weeks of drainage to a
16-cm water table depth after 1 week of flooding resulted in an organic
matter oxidation potential similar to flood in this lysimeter study. (Soil
Science 2004;169:600–608)