190 Growth Response of Four Tree Species to Fertilization and Humate Additives to CU Soil

in HortScience
Authors:
Jason Grabosky1Dept. of Environmental Horticulture, Univ. of Florida, Gainesville, FL 32611-0670; 2Cornell Univ., Dept. of Floriculture Ornamental Horticulture, Program Leader: Urban Horticulture Institute, Ithaca, NY 14853

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Nina Bassuk1Dept. of Environmental Horticulture, Univ. of Florida, Gainesville, FL 32611-0670; 2Cornell Univ., Dept. of Floriculture Ornamental Horticulture, Program Leader: Urban Horticulture Institute, Ithaca, NY 14853

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CU soil is a material primarily composed of clay loam soil and crushed stone designed for use under pavement to promote street tree root growth in a durable pavement section, such as sidewalks or parking lots. One concern is the low total soil fraction from which tree roots can meet nutritive demands. At issue is the long-term nutrient management of street trees once the root zone has been rendered inaccessible due to the pavement wearing surface, although in 3-year field tests, there were no differences found between a CU soil material and an agricultural field control. CU soil treatments were produced in a factorial design with a patent applied for processed humate additive, and a nursery production fertilization treatment. Bare-root seedlings of Salix nigra Marsh, Platanus × acerifolia Willd., Ginkgo biloba L., and cell plugs of Ficus benjamina L. were grown in treatment containers for 5 months. A Minolta SPAD-502 was used to evaluate relative chlorophyll content as an indication of leaf tissue nutrient levels. Plant growth as a function of new growth dry weight was calculated. Soil samples were collected at the end of the study and were analyzed to evaluate the impact of humate admixes in nutrient availability. The fertilization treatments positively influenced leaf color and growth for all species. The CU soil control plants displayed significantly lower chlorophyll levels, but overall growth differences were less dramatic—insignificant in some cases. The humate additive did not consistently affect leaf color. The humate additive alone did not affect plant growth, but a significant positive interaction with the fertilizer treatment was evident for Platanus and Ficus. The positive interaction was insignificant in Salix and non-existent in Ginkgo.

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