rootzone and gravel performance factors when intermediate layer is not required
A minimum 4" layer of 2 - 9.5 mm gravel is placed above the drain tile. The 12" rootzone mix is placed above the gravel.
particle size recommendations when the intermediate layer is used
A minimum 4" layer of gravel with ≥65% sized 1/4 - 3/8" is placed above the drain tile. A 2 - 4" layer of 1 - 4 mm Intermediate (Choker) Layer is placed above the gravel. The 12" rootzone mix is placed above the Intermediate Layer.
recommended particle size distribution for a putting green rootzone mixture
Physical properties of a rootzone mixture
USGA confidence intervals for quality control testing
The confidence interval for organic matter is an absolute value, not a percentage of the target organic matter content. For example, a rootzone mixture with a target organic matter content of 0.7 percent would have an acceptable range of 0.55 to 0.85 percent.