Water quality in the Everglades Agricultural Area (EAA) is influenced by the management of surface water and soils. Phosphorus release from organic soils in the EAA under long-term drained or intermittantly flooded soil conditions is not clearly understood. The purpose of this investigation was to study the effect of long-term (325 days) drained and flooded conditions on soluble P release measured on selected Florida Histosols. Five surface organic soils from the EAA were packed in columns and leached with 0.01 M CaCl2 followed by distilled water every 25 days for 1 year. Drained columns were incubated with a minus-NP solution after applying 100-cm water suction, while flooded columns were incubated using the same nutrient solution under a 3-cm depth flood. Repetitive flooding increased the amounts of total P and soluble reactive P (SRP) in leachates. Total P mineralized from flooded cultivated Histosols was up to two times higher than under drained cultivated conditions. Total P mineralized from an uncultivated Paho-kee flooded was 6.4 times higher than from the same uncultivated Histosol drained. Similar results were also observed in amounts of SRP mineralized under flooded and drained conditions. The Torry series was the only organic soil that showed no significant treatment differences in SRP or total P mineralized. A large percentage (55 to 90%) of the total P was mineralized in the form of SRP. The P mineralization rate ranged from 5.60 to 72.0 kg P ha-1 yr-1 for drained soils and from 36.0 to 87.9 kg P ha-1 yr-1 for flooded soils. Generally, P release rates decline with time. These results also indicate that higher P release occurs under periodic flooding and draining.
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Diaz et al. (1993) studied this question.