1O. A. Diaz, 2J. L. Pantoja, 3S. H. Daroub
1. South Florida Water Management District
2. Iowa State University
3. University of Florida
The Everglades agricultural area is composed by histosols laying on hard limestone bedrock in south Florida. Despite the common assumption of homogeneity of these soils, agricultural practices could result in the increase of soil variability. Therefore, soil spatial variability was studied on three fields (5.5 ha each) at the Everglades Research and Education Center to compare the changes in some chemical and physical soil properties due to agriculture and to determine the impact of cropping practices on such properties. When the study was conducted, the first field was under sugarcane, the second field was used for vegetable production, and the third field has never been cultivated nor fertilized. Soil depth to bedrock was recorded at each field (54 points per field following a triangular grid plan, 38.7 m between points). At each point a soil sample was collected (15 cm depth), and analyzed for pH, bulk density, moisture, soil organic matter (SOM) and extractable P, Ca, Mg, K and Si. Despite uniform topography, there was a substantial variability within and across fields. Tillage, flooding and application of fertilizers, resulted in an increase of variability in the concentration of nutrients. The mixing of bedrock material with the soil due to tillage, the traffic of agricultural equipment and the cleaning of ditches increased the soil bulk density, soil pH and some nutrients concentration, especially along roads and field ditches. Tillage also aerates the soil and accelerates SOM oxidation; however, when flooding the soil for cropping, the subsidence of these soils is reduced. Tilling the soil sometimes is a homogenizing factor, but in this study, the uncultivated field showed lowest variability in soil physical properties and nutrients concentration compared to the other two fields. Results confirm that agricultural activities have a great impact on soil variability in this area.
