An overview of historical development of shade-tree fertilization practices and current state of the art is presented. Research involving 6 shade tree cultivars and their response to 4 fertilizer formulations and 2 methods of application is reported. Test results show that on phosphorus deficient soil, broadcast application of a slow-release complete fertilizer yielded larger trees than any of the other treatments. Urea formaldehyde applied in 46 cm (18 in) deep holes stimulated shade tree development least. The section, Application of Research Findings, covers applications of the ‘Universal Tree Fertilization Calculation’ formula for determining the amount of fertilizer to apply per tree based on the radius of the root system.

The effect of container design on physical parameters of media with different bulk densities was evaluated. A significant interaction between container design and media for water-holding capacity and air space was found. A container with a polyester fabric bottom had the largest media air space and the smallest water-holding capacity after 24 h of drainage when placed on a column of sand to allow for free drainage from the container medium. For the media tested, a blend of composted pine bark and hardwood bark (PB:HB) appeared to have good physical characteristics for a container medium in the container designs that were evaluated. Container design should be considered when selecting a container medium because physical parameters of a given medium will be influenced.

The addition of peat-perlite to backfill soil increased the initial root movement through the backfill of transplanted holly (Ilex crenata Thunb. cv. Green Luster) grown in a peat-perlite medium. Backfill composition had no effect on the initial movement of roots of plants grown in a soil-peat-sand or pine bark-sand medium.

Shade tree research at the University of Tennessee, Knoxville, Tennessee showed that non-established, bare-root planted, shade trees did not respond to nitrogen fertilization but responded vigorously after establishment. Phosphorus and potassium levels above medium did not significantly increase growth. Growth rate increase due to nitrogen applications did not affect wood density and fiber length. Trees grown in high density groves and mulched with pea gravel on plastic had a higher growth rate than those in low density groves with grass as groundcover. Survival of bare-root transplanted shade tree species was not determined by type and amount of fertilization nor by method of application. On phosphorus deficient soils slow release 14-14-14, applied broadcast, gave a higher growth index for 5 out of 6 species tested than 14-14-14 applied in holes. Application of 20-20-20 soluble fertilizer was less effective. On soils containing sufficient phosphorus, surface application of nutrients was more effective than subsurface application while ammonium nitrate and 20-20-20 were equally effective.

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