Friday, 14 July 2006

Impact of Land Use on an Organic Soil of the Everglades Agricultural Area.

Ming Chen1, Samira Daroub2, Jose L. Pantoja3, Orlando Diaz1, Timothy A. Lang1, and Viviana Nadal1. (1) Everglades Res. & Educ. Center, University of Florida, 3200 E. Palm Beach Road, Belle Glade, FL 33430-8003, (2) Soil and Water Science Departemnt and Everglades Research and Education Center, University of Florida, 3200 E. Palm Beach Road, Belle Glade, FL 33430-8003, (3) Zamorano University, Agricultural Sci. and Production Dept., Fco. Morazán, 0093, Honduras

Cropping practices are important factors affecting soil variability in the organic soils of the Everglades Agricultural Area, which is an area of ~280,000 ha of highly productive organic soils south of Lake Okeechobee in Florida, USA. The objectives of this study were to (1) compare changes in soil properties of a Histosol that has been under different land uses; and (2) determine impacts of fertilization and cropping practices on selected chemical and physical properties of sugarcane, vegetable and virgin (uncultivated and unfertilized) fields located at the Everglades Research and Education Center of the University of Florida in Belle Glade, FL. Soil samples from the surface 15-cm of each field were taken using a triangular grid sampling plan. All samples were analyzed for bulk density, moisture, organic matter (OM) content, pH, total P, water extractable P (Pw), acid extractable P (Pa), Ca, Mg, K and Si. Correlation, ANOVA, factorial analyses and contour mapping were used to analyze the data. Soil pH increased significantly from 5.1 to 7.0 for the vegetable and sugarcane fields compared to the uncultivated virgin field. This is probably due to fertilizer including calcium silicate application to the crops and the mixing of organic matter with bedrock mineral materials high in CaCO3. Total P, Pw, Pa, and acid extractable Ca, Mg and Si were also significantly increased in the cropped fields. The shallowest soil depth (0.40 m), however, was found in the virgin and vegetable fields. The vegetable field showed the highest nutrient concentrations and lowest OM contents, followed by the sugarcane field. This is probably a result of soil oxidation, mixture of minerals, and fertilization. The shallow depth of the virgin field is probably due to the low water table maintained in that field and lack of irrigation. Soil parameters are highly correlated and can be categorized into three principal factors related to common agricultural practices in the EAA. We hypothesize that the change in properties in the cropped fields are due to an array of factors mainly mixing of mineral material from bedrock and roads, OM oxidation, water management including irrigation and depth of water table, and fertilization practices. Contour maps showed that the virgin field had the lowest variability for the majority of the properties measured.

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