Fate of phosphorus in Everglades agricultural soils after fertilizer application
- Everglades Research and Education Center, Belle Glade, FL (United States)
- Univ. of Florida, Gainesville, FL (United States)
Land use changes, agricultural drainage and conventional cultivation of winter vegetables and sugarcane cropping in the Everglades Agricultural Area (EAA) may alter soil conditions and organic matter decomposition and ultimately influence the fate of phosphorus (P). Theses agricultural practices promote soil subsidence, reduce the soil depth to bedrock limestone and increase the potential for incorporation of limestone into the root zone of crops. The incorporation of limestone into surface soil has significantly increased soil pH which in turns causes greater fixation of P fertilizer into unavailable forms for plant growth. Additional P fertilization is thus required to satisfy crop nutrient requirements in plant-available P form. It is important to determine how the mixing of bedrock limestone into soils influences the behavior of P fertilizers after their application. To accomplish this task, P fertilizers were applied to (1) typical cultivated soils and to (2) soils that have never been fertilized or extensively tilled. The changes in P concentrations over time were then compared between the two land uses, with differences being attributable to the impacts of cultivation practices. The P distribution in soil varied between land uses, with sugarcane having more P in inorganic pools while the uncultivated soil had more in organic pools. Water-soluble P concentrations in soil increased with increasing fertilizer application rates for all sampling times and both land uses. However, concentrations in uncultivated soil increased proportionally to P-fertilized soil due to organic P mineralization. At all sampling times, plant-available P concentrations remained higher for uncultivated than sugarcane soil. Lower P concentrations for sugarcane were related to adsorption by mineral components (e.g. limestone). Cultivated soils have higher calcium concentrations resulting from incorporation of bedrock limestone into soil by tillage, which increased pH and fostered sequestration of plant-available P into stable calcium-bound P pools. This greater P retention for sugarcane was reflected in the greater proportion of P in inorganic pools compared to uncultivated soils. Some lands within the EAA, including wetlands and seasonally-flooded prairies, are being reclaimed for water quality purposes. However, long-term effects of fertilization and cropping practices described in this document indicate that direct conversion from active farming, such as from sugarcane production directly to wetlands, may be problematic due to the changes in nutrient dynamics that may occur. The shift directly to wetlands may, in fact, release considerable amounts of P into the Everglades, thwarting the intent of the land use change. The inorganic P component in sugarcane soils may lead to the regeneration of soluble P in frequently flooded land uses such as wetlands. While most of the inorganic P pools are unavailable to sugarcane, the direct conversion of sugarcane soils to wetlands may facilitate P release. Here, reclamation of sugarcane fields for environment uses would benefit by an intermediate step to allow for a short duration of seasonal flooding allowing for P conversion from inorganic to organic forms. Prolonged flooding of organic soils previously used for intensive agriculture is not recommended.
- Research Organization:
- Intelligentsia International, LaBelle, FL (United States)
- Sponsoring Organization:
- USDOE Office of Energy Efficiency and Renewable Energy (EERE), Sustainable Transportation Office. Bioenergy Technologies Office
- DOE Contract Number:
- EE0000303
- OSTI ID:
- 1337876
- Report Number(s):
- DOE-HENDRYFLA-00303-219; EDIS-SL290
- Resource Relation:
- Related Information: Electronic Data Information Source (EDIS) of UF/IFAS Extension, publication number SL290
- Country of Publication:
- United States
- Language:
- English
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