Masters Theses

Date of Award

8-1986

Degree Type

Thesis

Degree Name

Master of Science

Major

Landscape Architecture

Major Professor

Willard T. Witte

Committee Members

Hendrik van de Werken, Ken Tilt, G. Douglas Crater

Abstract

This research consisted of a series of experiments designed to study the preparation and use of blended pine and hardwood bark as a container growing medium. The first experiment studied the influence of composting on the preparation of blended hardwood and pine bark media, and the succeeding experiments studied plant growth in the media prepared in the first experiment.

2.72 m3 piles of hardwood bark, pine bark, and 75:25, 50:50, and 25:75 (percent by volume) blends of hardwood and pine bark were composted using a partitioned windrow. Differing amounts of fertilizer amendments including urea, potassium nitrate, superphosphate, iron sulfate, and sulfur were added before composting prorated on the amount of hardwood bark in the medium. Daily heat production during composting was measured and used to determine when stabilization was achieved. Changes in physical and chemical properties were recorded. For comparison with blends mixed before composting, three additional groups of 75:25, 50:50, and 25:75 blends were formed by mixing composted hardwood bark with composted pine bark, composted hardwood bark with noncomposted pine bark, or fresh hardwood bark with noncomposted pine bark. The two control media were a 50:50 (percent by volume) blend of noncomposted pine bark and spent mushroom compost, and a 3:1:1 (by volume) blend of noncomposted pine bark:peat:river sand, which is a standard nursery medium. Physical and chemical properties were compared between blends mixed before or after composting, and between hardwood and pine bark media and control media.

Pine bark and hardwood bark amended with 50% or 75% pine bark stabilized before 100% hardwood bark. Based upon the time to stabilization in hardwood and pine bark, the 50:50 blend stabilized before expected. Based on the terminal volume of hardwood and pine bark, shrinkage in blended media was less than expected. Since the 50:50 blend stabilized sooner with comparatively less shrinkage, it appeared to be the most efficient blend of hardwood and pine bark for composting. All media had acceptable physical properties, except for the low air capacity of the 3:1:1 control. Physical and chemical properties did not differ between blends containing composted hardwood bark mixed before or after composting.

Euphorbia pulcherrima Willd. ex Klotzch 'Gutbier V-14 Glory', Pelargonium X hortorum L.H. Bailey 'Aurora', Chrysanthemum X morifolium Ramat. 'May Shoesmith', Ilex crenata Thunb. 'Hetzii', and Rhododendron hybrid 'Red Ruffles' were grown in the previously described media. Root rot, manganese toxicity, and nitrogen, iron, copper, or boron deficiencies variously influenced the growth of these crops. Plants grew as well in treebark media as in the control media. Growth was the same in composted hardwood bark, composted pine bark, and noncomposted pine bark, showing that there is no need to compost pine bark, and that composted hardwood bark is a suitable substitute for pine bark. Growth did not differ between blended media mixed before or after composting. Several species grew better in 50:50 blends than in the control media. Azaleas grown in media containing fresh hardwood bark grew as well as control media, indicating that hardwood bark may not need to be composted before use as a container medium component. Since the 50:50 blend finished composting before expected with more volume than expected, and frequently produced better growth than control media, it appeared to be an excellent medium for container nursery production systems.

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