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Title: Land application of carbonatic lake-dredged materials: Effects on soil quality and forage productivity

Author
item Sigua, Gilbert
item Coleman, Samuel
item HOLTKAMP, MIKE - S.W. FLA. WATER MGT. DIST

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/17/2006
Publication Date: 9/12/2006
Citation: Sigua, G.C., Coleman, S.W., Holtkamp, M.L. 2006. Land application of carbonatic lake-dredged materials: Effects on soil quality and forage productivity. Journal of Environmental Quality. 35:1784-1794.

Interpretive Summary: A four-year (2001-2005) study on land application of carbonatic lake-dredged materials (CLDM) as an option for disposal was conducted on a beef cattle pasture in south central Florida. Forage production may offer an alternative disposal since nutrients in the CLDM are recycled into crops that are not directly consumed by humans. The objectives of this study were: (1) to assess CLDM as a soil amendment to improve quality of sandy soils in most subtropical beef cattle pastures; and (2) to determine the effect of CLDM on productivity and nutritive values of bahiagrass (BG) in subtropical beef cattle pasture. Beneficial uses CLDM are both economical and environmental. Results of our study have demonstrated the favorable and beneficial effects of added CLDM on the early establishment of BG and soil quality in pasture fields. Often these materials can be obtained at little or no cost to the farmers or landowners in south Florida. Bahiagrass in plots that were treated with CLDM had significantly higher forage yield and crude protein when compared with those BG in the control plots. Results showed that CLDM can be used as soil amendments (lime and fertilizer) for early establishment of BG in beef cattle pastures. Environmentally, dredging of sediments that are rich in CaCO3 should restore the 19.4-sq km LP by removing natural sediments from the lake bottom to improve the fishery, water quality, and navigation of the lake.

Technical Abstract: Productive disposal options of carbonatic lake-dredged materials (82% CaCO3) may provide substantial and intangible benefits that will enhance the environment, community, and society. 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 (2001-2005) study on land application of CLDM as an option for disposal was conducted on a beef cattle pasture in south central Florida. Forage production may offer an alternative disposal since nutrients in the CLDM are recycled into crops that are not directly consumed by humans. The objectives of this study were: (1) to assess CLDM as a soil amendment to improve quality of sandy soils in most subtropical beef cattle pastures; and (2) 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- (1,000 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: 1,000 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: (1) lower penetration resistance; (2) an increase in soil pH and exchangeable cations (Ca and Mg); and (3) 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.