I just added a spare Qsoil to base in a plot that I will water. My goal is to characterize the behavior of an EC-5 probe in this soil with high iron content. Hopefully, it will still have a slope of 1, but just an offset. Although the soil structure changes a bit from site-to-site here, the iron content appears (based on my magnet test) to be about the same at base as at near, so I am optimistic that these test results will be relevant to the other sites.
Probe is ECHO005/PIC015.
The plan is simply to water this plot to field capacity and watch it dry out, while taking gravimetric samples regularly -- at least daily.
15:00 took the first sample (still before wetting; soil was a little bit moist). I'll just measure the 3-6cm ring, as being close to the location of the EC5 (volume = 3*pi*(5.31/2)^2 )
10/25: 09:35 First watering. Water ponded. I'll wait a bit and reapply.
09:45 Second watering. EC5 still hasn't seen it.
10:00 Water #3. EC5 still hasn't seen it.
10:15 Water #4. EC5 noticeably rising.
10:45 Water #5. EC5 up quite a bit.
11:05 Water #6.
11:15 Water #7. I'll stop here.
11:40 EC5 beginning to flatten out.
Date | Time | Tare | Wet | Dry | Rho | Grav% | Vol% | EC-5 |
|---|---|---|---|---|---|---|---|---|
10/24 | 15:00 | 2.4 | 84.3 | 77.8 | 1.14 | 8.3% | 9.5% | 9.5% (EXACT!) |
10/25 | 13:30 | 8.2 | 129.0 | 111.0 | 1.55 | 17.5% | 27.1% | 20.3% |
10/25 | 16:45 | 8.2 | 117.0 | 102.8 | 1.42 | 15.0% | 21.4% | 18.6% |
10/26 | 11:00 | 8.2 | 108.3 | 98.1 | 1.35 | 11.3% | 15.4% | 17.1% |
10/27 | 09:15 | 8.2 | 102.6 | 92.9 | 1.27 | 11.5% | 14.6% | 14.2% |
10/27 | 13:25 | 8.2 | 128.8 | 115.2 | 1.61 | 12.7% | 20.5% | 15.7% |
10/28 | 16:30 | 8.2 | 141.0 | 126.7 | 1.78 | 12.1% | 21.5% | 14.2% |
10/29 | 15:20 | 8.2 | 109.3 | 98.3 |
|
|
| 13.3% |
Here is a plot of these data, along with a 1:1 line and a linear regression to all but the first sample (when the EC-5 might not have been settled in). The regression line has an intercept of 9.9% and a slope of 0.34. It was my intent that this slope would be applied to all of the METCRAXII Qsoil measurements, and to have the offset computed from the 1 or 2 gravimetric samples at each site.
