Particle Size Recommendations When the Intermediate Layer is Used
| Gravel Layer |
≤ 10% particles larger than 0.5 inch (12
mm)
≥ 65% particles between 0.250 inch (6.4 mm) and
0.375 inch (9.7 mm)
≤ 10% particles smaller than 2 mm |
| Intermediate Layer |
≥ 90% between 1 and 4 mm |
A 4" layer of 1/4 - 3/8" gravel 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
| PARTICLE |
DIAMETER |
SIEVE |
% BY WEIGHT
|
| Coarse gravel |
> 4 mm |
No. 5 |
0% |
Fine gravel
Very coarse sand |
2.0 - 3.4 mm
1 - 2 mm |
No. 10
No. 18 |
≤ 3% gravel
≤ 10% combined in this range |
Coarse sand
Medium sand |
0.5 - 1.0 mm
0.25 - 0.5 mm |
No. 35
No. 60 |
≥ 60% of the particles in this range |
| Fine sand |
0.15 - 0.25 mm |
No. 100 |
≤ 20% |
| Very fine sand |
0.05 - 0.15 mm |
No. 270 |
≤ 5% |
| Silt |
0.002 - 0.05 mm |
|
≤ 5% |
| Clay |
< 0.002 mm |
|
≤ 3% |
| Total fines |
Very fine sand + silt + clay |
|
≤ 10% combined |
| Coefficient of Uniformity (D60/D10) |
1.8 - 3.5
2.0 - 3.5
2.0 - 3.5 |
Rootzone mixtures with peat
Rootzone mixtures with inorganic amendments
Pure sand rootzone mixtures |
Physical Properties of a Rootzone Mixture
| PHYSICAL PROPERTY |
RECOMMENDED RANGE |
| Total Porosity |
35% - 55% |
| Air-filled Porosity |
15% - 30% |
| Capillary Porosity |
15% - 25% |
| Saturated Hydraulic Conductivity (Ksat) |
≥ 6 inches/hour (150mm/hr.) |
USGA Confidence Intervals for Quality Control Testing
| TEST PARAMETER |
USGA CONFIDENCE INTERVAL (%) |
| Fine gravel |
50 |
| Very coarse sand |
50 |
| Coarse sand |
15 |
| Medium sand |
15 |
| Fine sand |
15 |
| Very fine sand |
30 |
| Total porosity |
10 |
| Air-filled porosity |
15 |
| Capillary porosity |
15 |
| Saturated hydraulic conductivity |
25 |
| 1 Percent organic matter |
± 0.2 for mixes with > 1% OM
± 0.15 for mixes with ≤ 1% OM |
1 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.
USGA Recommendations for a Method of Putting Green Construction
|
