Master of Science (MS)


Plant, Environmental Management and Soil Sciences

Document Type



Bark is a renewable resource with limited availability as a medium used by the nursery industry. Previous research has indicated that pinebark and hardwood bark can be used as a substrate in nursery production. The objective of this study is to determine the effect of bark source (pinebark and hardwood bark), particle size distribution, and irrigation frequency on the growth and quality of azalea (Rhododendron indicum ‘Red Ruffle’), Indian hawthorn (Rhapeolepis indica ‘Snow’), and ligustrum (Ligustrum japonicum). Treatments were arranged in a factorial 6x2x2 plot design, with six soil mixes, two barks, two irrigation frequencies, and six blocks totaling 144 replicates. Treatments were arranged using a randomized complete block design. Pinebark and hardwood bark sources were sieved into four different categories using sieves 3.35mm (#6), 1.4mm (#14), 710µm (#25), and < 710µm (<#25) to establish uniform physical characteristics. Six treatments were established to provide media mixes of small, medium, and large particle size distributions. Irrigation treatments were based on the effluent collected after irrigation. Treatment 1 maintained an effluent level of 20 to 40%, while Treatment 2 maintained an effluent level of 10 to 20%. Results indicate that hardwood bark pH and EC were significantly greater than pinebark, although differences were minor (0.3 and 0.1 increase, respectively). Quality ratings of azalea, Indian hawthorn, and ligustrum were significantly greater in pinebark compared to hardwood bark (32%, 17%, and 33% increase, respectively). Also, growth index and shoot weights for azalea, Indian hawthorn, and ligustrum were significantly greater in pinebark compared to hardwood bark. Growth indexes increased 25%, 13%, 39%, respectively, and shoot weights increased 58%, 27%, 72%, respectively. Media treatment 3 (3.35mm, 710µm, < 710µm) produced the greatest shoot weights and growth index for azalea in pinebark. Media treatment 2 (3.35mm, 1.4mm, < 710µm) produced the greatest shoot weights, growth index, and quality ratings for Indian hawthorn and ligustrum. Hardwood bark particle size distribution had no significant effect on shoot weights, growth index, or quality ratings. Irrigation treatment 2 (low volume) significantly increased the values of EC and pH for all three plants.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Edward W. Bush