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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.

 

 

 

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