Today we measured green speed, surface firmness, hardness and soil moisture (at 3 inch depth) on two putting greens (both USGA sand) and at a sports turf area. The Clegg Impact Hammer (Clegg) tested hardness (Gmax) of the turf. Firmness was tested with the FieldScout TruFirm and the Firmness Meter (picture, left). Soil moisture was tested by the TDR 300 Soil Moisture Meter.
As you look at the data, please comment below on comparing putting green 1 (wet) versus putting green 2 (dry) based on the measurements. What do the numbers tell us? What can also account for the differences in stimp readings, as measured by the groups? You get 1 bonus point for commenting below!
Here is a summary of the three students groups results below:
| Putting Green 1 | |||||
| Group | Stimpmeter | Firmness Meter | TruFirm | Clegg | Soil Moisture |
| Morrison, Schneider, Shubitowski, Elum, Markin | 9 ft | 0.352in | 516 | 40 | 34 |
| Averman, Begley, Schroeder, Kim | 9ft | 0.307in | 634 | 36 | 35 |
| Powell, Hosket, Bernenbaum, Zevchik, Murrow, Spridgeon | 10ft | 0.325in | 559 | 41 | 4 |
| Putting Green 2 | |||||
| Group | Stimpmeter | Firmness Meter | TruFirm | Clegg | Soil Moisture |
| Morrison, Schneider, Shubitowski, Elum, Markin | 11ft | 0.630in | 359 | 122.6 | 4 |
| Averman, Begley, Schroeder, Kim | 13ft | 0.66in | 372 | 116 | 6 |
| Powell, Hosket, Bernenbaum, Zevchik, Murrow, Spridgeon | 14ft | 0.352in | 371 | 144 | 4 |
| Sports Turf | |||||
| Group | Stimpmeter | Firmness Meter | TruFirm | Clegg | Soil Moisture |
| Morrison, Schneider, Shubitowski, Elum, Markin | 3ft | 0.32in | 466 | 92 | 6 |
| Averman, Begley, Schroeder, Kim | 2ft | 0.272in | 843 | 80 | 6 |
| Powell, Hosket, Bernenbaum, Zevchik, Murrow, Spridgeon | 3ft | 0.26in | 843 | 83 | 11 |
I noticed on Green #1 that one group at a very low soil moisture measurement (4%) compared to the other two groups. This may be due to not pushing the soil moisture meter all the way down into the soil. The soil moisture measurement is taken for the entire area between the two probes. So if the probes are not pushed entirely down than the moisture meter is also measuring the moisture in the air, which would give a low reading.
It is clear that the firmness of the two putting greens was dictated by the level of moisture in the soil. The first putting green registered an average moisture of about 24 while the second putting green registered an average moisture of about 5. This large difference is evident in the firmness of the two greens, as the more moist green was a lot less firm and hard then the dryer green.
When using the Firmness meter, it is clear that the dry putting green is about twice as firm as the wet one which would account for the faster green speed.
The data says it all – one green had much less moisture than the other. The first green averaged a moisture of about 24 vs. an average moisture of 4 on the second green. The green with less-moisture was much more firm than the first green and therefore, had faster ball speed as well.
Looking at the numbers tells you that the harder, firmer, and dryer green (green 2 in this case) is the one where the ball is going to roll farther as evidenced by the Stimpmeter test. One thing that could affect readings is any grade difference on the greens. Our group noticed that on green 1 there was a slight runoff in one corner which would make the ball roll farther than it should.
This was a very unique project that we did. It was very interesting to see how everyone’s data was similar, yet a tad different. Green 2 was the best for ball roll, because it was the harder and firmer grass.