October 25, 2005 | General


BioCycle October 2005, Vol. 46, No. 10, p. 42
Florida trials analyze tree responses and economics of using MSW compost with fertilizer for growth of eucalyptus, cottonwood and cypress species.
D. L. Rockwood and D. R. Carter

A THREE-YEAR project at the University of Florida’s School of Forest Resources and Conservation addresses the need for economically feasible, practical solutions for applying recycled organics to fast-growing trees. Compost made with municipal solid waste and biosolids at the Sumter County, Florida Organics Recycling Center for Excellence (FORCE) facility was first applied to the forest crops at a research and demonstration study site near Sumterville in 2002-03. The FORCE study was doubled in size by planting over 2,000 trees in four cultural treatments in early 2004. These included plots comparing use of fertilizer, irrigation and/or compost on species including cottonwood, cypress and eucalyptus.
Our three-year research is extending preliminary findings to additional practical field applications of the “wet” form of compost in forestry, identifying market potential, and disseminating information about applications and field implementation. In previous studies, compost has considerably enhanced productivity of forest tree crops, namely cypress and fast-growing hardwoods such as cottonwood and eucalyptus. Compost-amended and bedded cypress trees were statistically taller and had two and 10 times more biomass than bedded-only and unbedded trees. Leaf and twig nitrogen concentrations were also higher in compost-amended trees, which also had more foliage and dense fine roots surrounding clumps of organic matter in the rhizosphere, suggesting potential for rapid future growth. Across the cypress studies, survival was noticeably greater with compost, ranging from 8 to 18 percent higher than noncompost treatments. When combined with applications of effluent and mulch, the compost applications produced an even higher growth response rate.
While the FORCE demonstration farm in Sumter County has been the primary demonstration area for the research, other sites have also been used for compost studies. About 290 tons of compost were applied in late January 2004 to a 3.4 acre cypress site near Brooksville, Florida in collaboration with the Florida Division of Forestry. Another study at Archer, Florida is evaluating the importance of compost in the phytoremediation of arsenic. Along with evaluating the impact of compost on tree crops, the Archer study has Chinese brake fern – an arsenic hyperaccumulator – in pure and mixed plots with and without compost as part of an intensive investigation to identify critical factors in cleaning up arsenic contaminated soil and groundwater throughout Florida. Another site at the Southwest Florida Research and Education Center near Immokalee is evaluating opportunities for growing trees with and without compost in the state’s vegetable producing sand lands.
In projects scheduled for the third quarter of 2005, compost will be applied to different study areas, and eucalyptus seedlings will be replanted. Measurements of tree height, pest incidence, survival and weather-induced responses will be taken. On-site environmental impacts of compost application will be monitored. As part of the overall analyses of the importance of input costs, planting configurations, rotation age, and market options in using compost on forest crops, yields and costs will be updated. A report on results will also be presented in a Compost Utilization session at the BioCycle Southeast Conference on November 15, 2005 in Charlotte, North Carolina.
D.L. Rockwood and D.R. Carter are with the University of Florida School of Forest Resources and Conservation in Gainesville.

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