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- Author or Editor: Mark A. Nash x
Component and particle-size effects on shrinkage of two-component potting media were determined. Milled pine bark-sand mixtures were used to determine particle-size effects on shrinkage. Shrinkage curves formed an inverted V with maximum shrinkage at the 1:1 (v/v) ratio. No shrinkage occurred when bark was mixed with bark or sand with sand. Shrinkage increased linearly in the range of 0% to 50% bark and decreased linearly in the range of 50% to 100% bark. Each half of the shrinkage curve was a mirror image of the other half. Shrinkage curves for peat-sand and peat-perlite were similar in form to that of bark-sand media.
Expanded shale and peat moss were mixed in 5 ratios and evaluated as potting media for Petunia and Impatiens. Two grades of shale (coarse and fine) were used. Bulk density increased linearly with increasing shale whereas total pore space and container capacity increased linearly with increasing peat. Air space of peat-fine shale was consistently lower than that of peat-coarse shale when the peat/shale ratio was the same. Container capacity of peat-fine shale was consistently higher than that of peat-coarse shale when the peat/shale ratio was the same. Growth and quality of both bedding plants increased quadratically with increasing peat in peat-coarse shale and increased linearly with increasing peat in peat-fine shale. Highest growth and quality of both plants were found in peat-coarse shale media with at least 50% peat and in peat-fine shale media with at least 75% peat.