Organic Matter Oxidation Potential Determination in a Periodically Flooded Histosol under Sugarcane

Histosols of the Everglades Agricultural Area (EAA) are subsiding primarily from aerobic microbial oxidation. An experiment was conducted in a Histosol to evaluate methods [ 14 C-benzeate oxidation (BO), soil respiration (CO 2 evolution; RESP), and microbial biomass carbon (MBC)] of determining short-term organic matter (OM) oxidation potential under alternate flood and drain management. Sugarcane (interspecific hybrids of Saccharum species) was grown in field lysimeters containing Pahokee muck soil (euic, hyperthermic Lithic Haplosaprist). Soils were flooded for 7 d followed by drainage to three depths (16, 33, and 50 cm) for 14 d. A continuously drained control treatment was also included. Thus, soils under four flood and drain cycles were sampled during the drain period. Increased water table levels after flooding reduced BO, tended to increase MBC, and had little effect on RESP. Consequently, BO was not correlated with either MBC or RESP, which suggests that microbes responsible for OM oxidation are a small portion of the total microbial population. Alternate flooding and draining increased BO compared with the drain control. Soil moisture (SM) and soluble organic carbon (SOC) were both negatively correlated with BO, but not with either MBC or RESP. Soil moisture and SOC may provide alternate indicators for OM oxidation potential. Since BO responded according to soil OM oxidation on the basis of field measurements previously reported, BO was the best of the three methods for predicting short-term effects of water table management on soil OM oxidation potential.