THE USE OF BARK WASTE AS A SUBSTRATE IN HORTICULTURE

Growers of ornamental crops in the Southeast and the West Coast of the United States have used bark as a soil amendment or as a growth media in container growing. In the Southeast the Southern Pine species are used and on the West Coast the Redwood, the Douglas Fir, and the Western Red Cedar are the predominant trees harvested for lumber and pulp. Growers in the Northeast and Midwest have not until quite recently utilized bark as a soil amendment. In this area the trees harvested are hardwood species such as Oak, Hickory, Maple, Walnut, and Ash. In the past there was considerable speculation that bark and sawdust of hardwood species was toxic and growers were afraid to use these materials as soil amendments.

Recently, with the emphasis on ecology, new laws were enacted and producers of bark wastes could no longer dump or burn these residues. Therefore, they were interested in finding other ways of disposing of these wastes. Growers of ornamental crops have become more interested in artificial growth media. Growers of nursery crops are starting to switch to container growing as labor and land prices increase. Sphagnum peat and sand have been looking for substitutes since the cost of sphagnum peat is steadily increasing.

In 1966, Boxley (3), a commercial grower reported success in growing rhododendrons in well-aged bark of hardwood species at the plant propagators meeting held in Biloxi, Mississippi. This interested Midwest growers in the use of hardwood barks as a growth media. Upon search of literature, no information on the use of hardwood bark as a growth medium was found. Lunt and Clark (5), Allison (1) and Bolin (2) all reported success in using softwood species, primarily pine and fir as a soil amendment for container growing. The only problems they encountered was a suppression in growth from the lack of nitrogen.