Forest Growth Increased with Rockdust on Grandfather Mountain near Asheville, North Carolina, 1991

Dr. Robert Bruck

North Carolina State University

• 500 five-year-old red spruce and fraser fir trees were treated with Planters II rock dust applied at the following rates: 50-gram/pot, 25 g/pot, 10 g/pot, and 0 g/pot. After a 6-month period, observations were made on root color, diameters, height-growth, and survival.
• Survival rate of all rock-dusted trees was 100%, versus 87% of fraser fir and 77% of spruce of the controls.
• Growth rate increases:
  • Red spruce were 37, 18, and 5 percent.
  • Fraser fir were 39, 21, and 14 percent.

Field experiments, 1991
Results after 12 weeks in study on Grandfather Mountain near Asheville, North Carolina, where 6,000 red spruce and fraser fir seedlings were planted at 5,500-ft. elevation. The plots were split in half, and 175 lb. per acre of Planters II broadcast on each split-plot of fraser fir and red spruce, respectively; the other split-plot received no treatment.

• Height growth of red spruce was increased by 27 percent over nontreated controls.
• Height growth of fraser fir was 19 percent greater than untreated controls.

General appearances of treated trees was that of a very dark green color and good flushing of 1991 tissues, whereas untreated controls appeared to be somewhat yellow and chlorotic.