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TECHNICAL REPORTS

Organic Compounds in the Environment

Land Application of Carbonatic Lake-Dredged Materials

Effects on Soil Quality and Forage Productivity

^a USDA-ARS, Subtropical Agricultural Research Station, Brooksville, FL 34601
^b Southwest Florida Water Management District, Tampa, FL 33637

^* Corresponding author (gcsigua{at}ifas.ufl.edu)

Received for publication February 13, 2006. The ability to reuse carbonatic lake-dredged materials (CLDM) for agricultural purposes is important because it reduces offshore disposal and provides an alternative to disposal of the materials in landfills that are already overtaxed. A four-year (2001 to 2005) study on land application of CLDM as an option for disposal was conducted on a beef cattle pasture in south central Florida. The objectives of this study were (i) to assess CLDM as a soil amendment to improve quality of sandy soils in most subtropical beef cattle pastures and (ii) to determine the effect of CLDM on productivity and nutritive values of bahiagrass (BG, Paspalum notatum Flügge) in subtropical beef cattle pasture. The five treatment combinations arranged in randomized complete block design were represented by plots with different ratios (R) of natural soil (NS) to CLDM: R1 (1000 g kg^–1:0 g kg^–1); R2 (750 g kg^–1:250 g kg^–1); R3 (500 g kg^–1:500 g kg^–1); R4 (250 g kg^–1:750 g kg^–1); and R5 (0 g kg^–1:1000 g kg^–1). Addition of CLDM had significant (p 0.001) effects on soil quality and favorable influence on forage establishment and nutritive values. Compared with the control plots (0 g kg^–1), the soils in plots amended with CLDM exhibited (i) lower penetration resistance, (ii) an increase in soil pH and exchangeable cations (Ca and Mg), and (iii) decrease in the levels of soil trace metals (Mn, Cu, Fe, Zn, and Si). Results disclosed consistently and significantly (p 0.001) higher BG biomass production (forage yield = –106.3x² + 1015.8x – 39.2; R² = 0.99**) and crude protein content (CP = 1.24x + 6.48; R² = 0.94**) from plots amended with CLDM than those of BG planted on plots with no CLDM treatment.

Abbreviations: ANOVA, analysis of variance • BG, bahiagrass • CLDM, carbonatic lake-dredged materials • CP, crude protein content • DMRT, Duncan multiple range test • DMY, forage dry matter yield • GLM, general linear model • LP, Lake Panasoffkee • LSD, least significant difference • n, number of samples • NS, natural soils • PEL, probable effects level • SAS, statistical analysis system • SWFWMD, Southwest Florida Water Management District • TEL, threshold effects level • TIN, total inorganic nitrogen • TN, total Kjeldahl nitrogen • TP, total phosphorus