Journal of Analytical Sciences, Methods and Instrumentation, 2013, 3, 137-151
http://dx.doi.org/10.4236/jasmi.2013.33017 Published Online September 2013 (http://www.scirp.org/journal/jasmi)
137
A Study on Measurement of Forest Soil Redox Potential
Mu Liu1,2, Chengde Luo1, Xiaoyun Liu2, Gang Wan2, Bin Dai1
1College of Forestry, Sichuan Agricultural University, Ya’an, China; 2Promotion Center of Forestry Technology, Forestry Bureau of
Fushun County, Fushun, China.
Received June 5th, 2013; revised July 9th, 2013; accepted July 28th, 2013
Copyright © 2013 Mu Liu et al. This is an open access article distributed under the Creative Commons Attribution License, which
permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
ABSTRACT
Redox potential has principal influences on formation and attribute of soils, so it is necessary to research the measure-
ment of soil redox potential. The self-made potentiometer and two indigenous FJA-5 potentiometers were employed to
measure the Eh values of fir forest soils in situ, which lay in Savage Sea Beauty Spot in Sichuan Province. Simultane-
ously fresh soils in situ were collected and made into suspensions with various soil-water ratios and standing time to
measure Eh values. The results demonstrated that the total tendency of Eh values measured by the self-made potenti-
ometer was gradually falling with soil-water ratios increasing and standing time prolonging. There is a great difference
between Eh values measured in laboratory and in situ. Only in situ may the measured Eh values show realistic oxida-
tion-reduction conditions and formation characteristics of forest soil. The self-made potentiometer has a more preferable
performance than indigenous FJA-5 potentiometers and it can be applied to measuring forest soil Eh in situ.
Keywords: The Self-Made Potentiometer; Redox Conditions; Suspensions; Soil-Water Ratios and Standing Time
1. Introduction
Redox reaction is one of the most basic forms of material
motion in nature and a vital dynamic phase in soil forma-
tion. Redox potential is an intensity index, which decides
the direction and extent of redox reaction, and is used for
estimating soil’s redox ability and showing clearly mor-
phological characteristics and mobile performance of
mineral elements in soil profile [1]. So far, Eh value has
been mostly measured in soft hydromorphic soils, such
as paddy soil [2-11]. For unhydromorphic soils, their Eh
values were usually measured after the soil was made
into suspensions or disposed else [12-21]. However there
are fewer researches on measurement of the forest soil
redox potential. The environment and substance compo-
sition of soil itself have an extremely profound impact on
redox potential, so it is important to research the methods
and technologies about measurement of forest soil Eh.
2. Materials and Methods
2.1. Developing Redox Potentiometer Alone
At present most of redox potentiometers made in China
are matched with acidimeters. They are usually used to
measuring pH and Eh in soil solution. Sometimes they
contribute to detect Eh values in paddy soils or other soft
sediment. Hence the special redox potentiometer for the
forest soil Eh was made by ourselves and its measured
results would be compared with the indigenous FJA-5
potentiometers’ results.
A self-developed platinum electrode, a commercially
available saturated calomel electrode and a DT-9205B
multimeter were combinated into the self-made potenti-
ometer (Figure 1). It is necessary to adjust the potential
of platinum electrode before measurement so that exact
and stable Eh values can be obtained [22-25]. In addition
the sand core lies in bottom of saturated calomel elec-
trode should be slightly immersed in saturated KCl to
decrease the disturbance of liquid junction potential as
far as possible [26,27].
2.2. Experimental Design
There were two experiments, namely, in situ test and
laboratory test. In situ test was achieved in Savage Sea
Beauty Spot in Sichuan Province, where the soil under fir
forest was tested. The soil layer was respectively Layer
Ad, the biggest eluvial horizon, and Layer B2, the biggest
illuvium. Eh values were measured in February 2011.
Electrodes of the self-made potentiometer and FJA-5
potentiometers were inserted in the central section of
Layer Ad and the electrodes of self-made potentiometer

A Study on Measurement of Forest Soil Redox Potential 138
Figure 1. The schematic diagram of the self-made redox
potentiometer.
were between that of two FJA-5 potentiometers. And
what’s more, the distance between platinum electrode
and saturated calomel electrode ought to be near (1 - 3
cm), which could lower the resistance and determinate
error.
Opened the power supply of DT-9205B multimeter
linked with the self-made potentiometer and record the
numerical value in display screen after it was stable.
When the amplitude of fluctuation of the numerical value
was less than 1 mv in five minutes, the value was
deemed to be stable. Here it was emphasized that the
numerical value in display screen only meaned the po-
tential difference between platinum electrode and satu-
rated calomel electrode instead of Eh value. The Eh val-
ue must be the summation of this potential difference and
the constant potential provided by saturated calomel
electrode at corresponding temperature. Simultaneously
opened the power supply of FJA-5 potentiometers and
the numerical value in display screen was exactly the Eh
value. After finishment of Eh measurement in Layer Ad,
all electrodes were taken out and washed by distilled
water, then they were cleaned by dry filter papers to con-
tinue measuring Eh values of Layer B2 with the same
method. Eh values of each layer were repeatedly meas-
ured three times. Furthermore fresh soil of both Layer Ad
and Layer B2 were collected, preserved with fresh-keep-
ing packaging and brought back to laboratory.
10 g fresh soil samples were weighed and put in 50-ml
beakers with high pattern in which additional distilled
water with different volumes were mixed and suspend-
sions with different soil-water ratios were formed. These
suspensions had five soil-water ratios together, that was,
1:1, 1:2, 1:3, 1:4 and 1:5. As far as they were formed, the
standing time was began to be recorded, which was re-
spectively 0, 1, 2, 6, 12, 24, 48, 96, 144, 192 and 240
hours. Then Eh values were measured under varied soil-
water ratio and standing time by the self-made poten-
tiometer and FJA-5 potentiometers. As same as in situ
test, Eh values were repeatedly measured three times. At
last average values were worked out to draw the curve
graph where Eh values were changing with changed soil-
water ratios and standing time.
3. Results and Discussion
3.1. Laboratory Analysis
The Eh values measured by the self-made potentiometer
were gradually falling with soil-water ratios increasing
and standing time prolonging (Figure 2), whereas the Eh
values measured by FJA-5 potentiometers were some-
times high and sometimes low, and irregular (Figures 3
and 4). The approximate tendency of Eh values of vari-
ous suspensions with incremental soil-water ratios and
prolonged standing time could be analysed according to
Nernst Equation
0RT OX
Eh ELOG
nF RED
=+ [28].
If soil-water ratio is smaller, the concentration of re-
dox systems in soil is higher, the oxidizing matters’ oxi-
dation capability is more powerful, even the concentra-
tion of oxidizing matters (OX) is greater than that of re-
(a)
(b)
Figure 2. The variational curves of Eh values in Layer Ad (a)
and Layer B2 (b) measured by the self-made potentiometer.
1:1, 1:2, 1:3, 1:4 and 1:5 were the soil-water ratios.

A Study on Measurement of Forest Soil Redox Potential 139
(a)
(b)
Figure 3. The variational curves of Eh values in Layer Ad (a)
and Layer B2 (b) measured by the first FJA-5 potentiometer.
1:1, 1:2, 1:3, 1:4 and 1:5 were the soil-water ratios.
(a)
(b)
Figure 4. The variational curves of Eh values in Layer Ad (a)
and Layer B2 (b) measured by the second FJA-5 potenti-
ometer. 1:1, 1:2, 1:3, 1:4 and 1:5 were the soil-water ratios.
ducing matters (RED), then the Eh value is higher.
However, with soil-water ratio amplifying, the concen-
tration of redox systems is decreasing little by little, the
reducing matters’ reduction capability is just improving
and this moment the concentration of reducing matters
(RED) will exceed the oxidizing matters (OX), as a result
the Eh value is falling by degress. Furthermore soil is
isolated from the atmosphere outside more and more
seriously when standing time is infinitely prolonging, the
reduction condition is more and more superior, and then
the concentration of reducing matters (RED) is more and
more greater. Thereupon the Eh value will be more and
more lower.
From what had been analysed above, the approximate
tendency of Eh values measured by the self-made poten-
tiometer was coincident with the consequence deduced
from Nernst Equation, while the total trend of Eh values
detected by FJA-5 potentiometers was not. Willis (1932),
Quispel (1947) and Bohn (1968) considered consensually
that Eh was related to water levels, moisture content, soil
structure and the amount of oxidational and reducible
materials as well as it was only possible to detect oxida-
tion-reduction conditions in soils when the measure-
ments were carried out in situ after making Eh measure-
ments on soil pastes or suspensions [18,29,30].
3.2. In Situ Analysis
Eh values measured in situ were showed by Table 1. In
order to examine the precision and reappearance, coeffi-
cient of variation was employed. It was noticed that ‘0’
(Table 1) should not be involved in averaging when cal-
culating coefficient of variation.
It was clear in Table 1 that coefficient of variation of
Eh values got from the self-made potentiometer was
much less than 1%, while that of values got from FJA-5
potentiometers was much bigger. Thus it was considered
that the measurement results of the self-made potenti-
ometer had relatively higher precision and better reap-
pearance.
Soil redox potential is closely related to moisture, po-
rosity, ventilated extent and content of organic matter
[1,6,9], so them of soil in situ were revealed in Table 2.
Seen from which, the contents of moisture and organic
matter in Layer Ad were obviously higher than that of
Layer B2, as well as porosity and ventilated extent were
smaller than that of Layer B2, thereupon the Eh value of
Layer Ad ought to be lower than Layer B2. From what
Table 1 showed, the Eh values of Layer Ad measured by
the self-made potentiometer were all lower than Layer B2,
while the results got from FJA-5 potentiometers were
Table 1. Soil Eh values measured in situ.
Soil LayerEh Values, mv Coefficient of
Variation, %
Ad △ 585.6 384.7 595.2 22.78
○ 386.1 385.1 386.1 0.15
▽ 520.6 459.7 0 8.59
B2 △ 323.7 285.5 337.4 8.52
○ 494.8 494.8 493.8 0.12
▽ 377.9 311.3 0 9.66
△, Eh values measured by the first FJA-5 potentiometer; ○, Eh values
measured by the self-made potentiometer; ▽, Eh values measured by the
second FJA-5 potentiometer.
Table 2. Soil moisture, porosity, ventilated extent and con-
tents of organic matter.
Soil
Layer Moisture, %Porosity, % Ventilated Extent, %
Contents of
Organic Matter, %
Ad 33.64 40.6 22.77 5.3556
B2 12.35 49.72 28.65 1.3484

A Study on Measurement of Forest Soil Redox Potential 140
opposite. It has been proved that oxidation processes
occupy primary superiority in formation of forest soil,
however moisture and organic matter often accumulate in
surface layer so that redox potential of surface soil will
be lower than that of bottom soil [31]. This difference
may vary from several or dozens of millivolts to hun-
dreds of millivolts. Usually there is a buffer slightly in-
fluenced by moisture and organic matter below Layer A1,
such as Layer Ad [31]. In summary, Eh values measured
by the self-made potentiometer could objectively reflect
the oxidation-reduction conditions and formation char-
acteristics of forest soil in field.
The significance of difference between Eh values
measured by the self-made potentiometer and by FJA-5
potentiometers was tested. Similarly “0” (Table 1)
should not be involved in averaging and the test results
were displayed in Table 3. It was found in Table 3 that
the interclass differences (△ & ▽) were not significant
(P > 0.05) regardless of Layer Ad or B2, while in inter-
block differences, except that the difference between Eh
values of Layer Ad measured by the self-made po-
tentiometer and by the first FJA-5 potentiometer (○ & △)
was not significant (P > 0.05), the others were very
significant (P < 0.01). This test manifested that the
measurement results of the self-made potentiometer had
higher precision and accuracy than FJA-5 potentiometers.
The measurement results obtained from FJA-5 potenti-
ometers were hardly able to reflect the oxidation-reduce-
tion conditions and formation characteristics of soil in
field.
To move forward a single step, significance of differ-
ences between Eh values measured in situ and in labora-
tory by the self-made potentiometer were tested. The
result demonstrated that there was a significant (P < 0.05)
or very significant difference (P < 0.01) between Eh val-
ues measured in situ and at each soil-water ratio and
standing time in Layer Ad (Appendix 1), and that for
Layer B2, only exsited very significant difference (P <
0.01) (Appendix 2). So it is safely concluded that if for-
Table 3. Significance of differences of Eh values.
Soil Layer Source of Variation F P-value F crit
Ad Interblock ○ & △ 3.9554 0.1176 7.7086
○ & ▽ 35.5390** 0.0039 7.7086
Interclass
△ & ▽ 0.1959 0.6809 7.7086
B2 Interblock ○ & △ 136.7974** 0.0003 7.7086
○ & ▽ 55.9376** 0.0017 7.7086
Interclass
△ & ▽ 1.4266 0.2983 7.7086
△, Eh values measured by the first FJA-5 potentiometer; ○, Eh values
measured by the self-made potentiometer; ▽, Eh values measured by the
second FJA-5 potentiometer; **Significance of difference is at the P < 0.01
level.
est soils are brought back to laboratory and made into
suspensions for redox potential, there will be a great dif-
ference compared with the measurement in situ and the
Eh values measured in suspensions cannot completely
reflect the actual oxidation-reduction conditions of forest
soil.
4. Conclusions
For resreaches on redox process of unhydromorphic soils
such as forest soil, if soil samples are made into suspen-
sions, their Eh values will change with changed soil-
water ratio and standing time and it is difficult to deter-
mine appropriate soil-water ratio and standing time. The
Eh values measured at varied soil-water ratio and stand-
ing time have significant or very significant differences
with that measured in situ. So Eh measurement in situ
should be gradually promoted.
The methods and technologies about measurement of
unhydromorphic soil Eh in situ still need to face a lot of
problems and challenges in study on soil electrochemis-
try. Through preliminary analysis on Eh values measured
in situ and in laboratory, it can be definitely deemed that
the measurement results of the self-made potentiometer
have relatively higher precision and accuracy and that the
self-made potentiometer can be applied to measuring
forest soil Eh in situ.
5. Acknowledgements
The authors thank Prof. Yongxin Zhan and Prof. Liang
Zhao (Department of Physics, College of Life and Basic
Sciences, Sichuan Agricultural University) for guiding
make of redox potentiometer.
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A Study on Measurement of Forest Soil Redox Potential 142
Appendix 1
Significance of differences between Eh values measured in situ and in laboratory (Layer Ad).
Source of Variation
Soil-water Ratio Standing Time,
hours Suspension Eh In situ Eh
F P-value F crit
360.9 386.1
360.9 385.1
0
361.9 386.1
2708.48** 8.1589E-07 21.1977
363.1 386.1
362.1 385.1
1
363.1 386.1
2380.50** 1.0558E-06 21.1977
363 386.1
361 385.1 2
361 386.1
1045.46** 5.4547E-06 21.1977
357.1 386.1
357.1 385.1 6
357.1 386.1
7396.00** 1.0959E-07 21.1977
342 386.1
342 385.1 12
342 386.1
17239.69** 2.018E-08 21.1977
343 386.1
344 385.1 24
343 386.1
8102.65** 9.1315E-08 21.1977
320.9 386.1
320.9 385.1 48
320.9 386.1
37869.16** 4.1832E-09 21.1977
286.5 386.1
286.5 385.1 96
286.5 386.1
88684.84** 7.6282E-10 21.1977
262 386.1
262 385.1
144
262 386.1
137863.69** 3.1567E-10 21.1977
251.3 386.1
251.3 385.1 192
251.3 386.1
162731.56** 2.2656E-10 21.1977
250 386.1
250 385.1
1:1
240
251 386.1
82539.85** 8.8062E-10 21.1977

A Study on Measurement of Forest Soil Redox Potential 143
Continued
407.2 386.1
407.2 385.1
0
407.2 386.1
4134.49** 3.50435E-07 21.1977
402 386.1
402 385.1
1
402 386.1
2371.69** 1.06369E-06 21.1977
384.7 386.1
384.7 385.1
2
384.7 386.1
10.24* 0.03290081 21.1977
388 386.1
389 385.1
6
389 386.1
37.84** 0.00354206 21.1977
371.7 386.1
371.7 385.1
12
371.7 386.1
1780.84** 1.88485E-06 21.1977
360 386.1
361 385.1 24
360 386.1
2910.85** 7.06511E-07 21.1977
338.1 386.1
338.1 385.1
48
339.1 386.1
10082.00** 5.8989E-08 21.1977
298 386.1
299 385.1 96
299 386.1
34138.85** 5.14717E-09 21.1977
247.2 386.1
247.2 385.1
144
247.2 386.1
172806.49** 2.00916E-10 21.1977
238 386.1
238 385.1 192
238 386.1
196514.89** 1.55362E-10 21.1977
231.3 386.1
231.3 385.1
1:2
240
231.3 386.1
214739.56** 1.30111E-10 21.1977

A Study on Measurement of Forest Soil Redox Potential 144
Continued
346.1 386.1
346.1 385.1
0
346.1 386.1
14161.00** 2.9906E-08 21.1977
344 386.1
345 385.1
1
345 386.1
7601.45** 1.03748E-07 21.1977
346.2 386.1
346.2 385.1 2
345.2 386.1
7164.05** 1.16797E-07 21.1977
323.3 386.1
323.3 385.1 6
323.3 386.1
35118.76** 4.86397E-09 21.1977
298 386.1
298 385.1 12
299 386.1
34400.65** 5.06914E-09 21.1977
287.3 386.1
287.3 385.1 24
287.3 386.1
87261.16** 7.87909E-10 21.1977
288 386.1
287 385.1 48
287 386.1
43601.05** 3.15567E-09 21.1977
252.6 386.1
252.6 385.1 96
252.6 386.1
159600.25** 2.35541E-10 21.1977
249 386.1
250 385.1
144
250 386.1
83354.45** 8.63493E-10 21.1977
238.4 386.1
238.4 385.1 192
238.4 386.1
195452.41** 1.57056E-10 21.1977
197 386.1
197 385.1
1:3
240
197 386.1
320695.69** 5.83386E-11 21.1977

A Study on Measurement of Forest Soil Redox Potential 145
Continued
359.6 386.1
359.6 385.1 0
359.6 386.1
6162.25** 1.57835E-07 21.1977
359.6 386.1
359.6 385.1
1
359.6 386.1
6162.25** 1.57835E-07 21.1977
360 386.1
360 385.1 2
359 386.1
3065.45** 6.37119E-07 21.1977
351.8 386.1
351.8 385.1
6
351.8 386.1
10383.61** 5.56129E-08 21.1977
327 386.1
327 385.1
12
327 386.1
31081.69** 6.20939E-09 21.1977
326 386.1
327 385.1 24
326 386.1
15895.45** 2.37369E-08 21.1977
291.8 386.1
291.8 385.1
48
291.8 386.1
79467.61** 9.50024E-10 21.1977
262 386.1
261 385.1
96
261 386.1
69676.45** 1.23577E-09 21.1977
188.7 386.1
188.7 385.1
144
188.7 386.1
349517.44** 4.9114E-11 21.1977
186 386.1
187 385.1
192
187 386.1
178383.65** 1.88549E-10 21.1977
182.1 386.1
183.1 385.1
1:4
240
182.1 386.1
186050.00** 1.73331E-10 21.1977

A Study on Measurement of Forest Soil Redox Potential 146
Continued
335.3 386.1
335.3 385.1 0
335.3 386.1
22921.96** 1.14162E-08 21.1977
337.2 386.1
337.2 385.1
1
336.2 386.1
10760.45** 5.17871E-08 21.1977
335 386.1
335 385.1 2
335 386.1
23195.29** 1.11488E-08 21.1977
327.5 386.1
327.5 385.1
6
327.5 386.1
30555.04** 6.42526E-09 21.1977
302.4 386.1
302.4 385.1 12
302.4 386.1
62550.01** 1.53338E-09 21.1977
283.1 386.1
284.1 385.1
24
284.1 386.1
46818.00** 2.73693E-09 21.1977
290 386.1
291 385.1
48
291 386.1
40698.05** 3.62187E-09 21.1977
244 386.1
244 385.1 96
243 386.1
90865.85** 7.26638E-10 21.1977
201.5 386.1
201.5 385.1
144
201.5 386.1
305587.84** 6.42495E-11 21.1977
201 386.1
200 385.1 192
201 386.1
154179.05** 2.52396E-10 21.1977
195.4 386.1
195.4 385.1
1:5
240
195.4 386.1
326155.21** 5.64019E-11 21.1977
**Significance of difference is at the P < 0.01 level; *Significance of difference is at the P < 0.05 level.

A Study on Measurement of Forest Soil Redox Potential 147
Appendix 2
Significance of differences between Eh values measured in situ and in laboratory (Layer B2).
Source of Variation
Soil-water Ratio Standing Time,
hours Suspension Eh In situ Eh
F P-value F crit
412.1 494.8
411.1 494.8 0
412.1 493.8
30776.81** 6.333E-09 21.1977
410 494.8
410 494.8 1
410 493.8
64211.56** 1.4551E-09 21.1977
409.5 494.8
410.5 494.8
2
409.5 493.8
32232.61** 5.7739E-09 21.1977
385.5 494.8
385.5 494.8
6
385.5 493.8
106863.61** 5.2537E-10 21.1977
375 494.8
375 494.8 12
375 493.8
128450.56** 3.6363E-10 21.1977
337.2 494.8
338.2 494.8 24
337.1 493.8
105093.27** 5.4322E-10 21.1977
346.6 494.8
347.6 494.8 48
346.6 493.8
97947.38** 6.2537E-10 21.1977
316.4 494.8
317.4 494.8 96
316.4 493.8
142151.12** 2.969E-10 21.1977
282 494.8
281 494.8
144
281 493.8
204416.18** 1.436E-10 21.1977
268.4 494.8
268.4 494.8
192
268.4 493.8
459955.24** 2.836E-11 21.1977
261 494.8
262 494.8
1:1
240
261 493.8
244580.18** 1.003E-10 21.1977

A Study on Measurement of Forest Soil Redox Potential 148
Continued
376.3 494.8
376.3 494.8 0
376.3 493.8
125670.25** 3.799E-10 21.1977
377 494.8
378 494.8
1
378 493.8
61390.08** 1.592E-09 21.1977
374.7 494.8
373.7 494.8 2
373.7 493.8
65268.85** 1.408E-09 21.1977
352.6 494.8
353.6 494.8 6
352.6 493.8
90142.58** 7.383E-10 21.1977
349 494.8
350 494.8 12
349 493.8
94786.58** 6.678E-10 21.1977
312.2 494.8
312.1 494.8
24
312.1 493.8
296246.53** 6.837E-11 21.1977
306.3 494.8
306.3 494.8 48
306.3 493.8
318660.25** 5.909E-11 21.1977
278 494.8
278 494.8
96
278 493.8
421720.36** 3.374E-11 21.1977
278.1 494.8
277.2 494.8 144
277.1 493.8
221885.34** 1.219E-10 21.1977
261 494.8
262 494.8 192
261 493.8
244580.18** 1.003E-10 21.1977
258 494.8
259 494.8
1:2
240
258 493.8
250915.28** 9.53E-11 21.1977

A Study on Measurement of Forest Soil Redox Potential 149
Continued
346.8 494.8
346.7 494.8 0
346.8 493.8
194393.67** 1.588E-10 21.1977
346.9 494.8
346.9 494.8
1
347 493.8
193955.21** 1.595E-10 21.1977
345.3 494.8
345.3 494.8
2
345.3 493.8
200256.25** 1.496E-10 21.1977
342.1 494.8
342.1 494.8 6
342.1 493.8
208940.41** 1.374E-10 21.1977
317.3 494.8
317.3 494.8 12
317.4 493.8
279590.06** 7.675E-11 21.1977
324.1 494.8
324.1 494.8 24
324.1 493.8
261223.21** 8.793E-11 21.1977
320.1 494.8
320 494.8
48
320 493.8
271131.57** 8.162E-11 21.1977
281.5 494.8
281.5 494.8
96
281.6 493.8
404025.19** 3.676E-11 21.1977
279.3 494.8
279.3 494.8
144
280.3 493.8
207690.13** 1.391E-10 21.1977
243 494.8
243 494.8
192
243 493.8
569119.36** 1.852E-11 21.1977
239.2 494.8
239.2 494.8
1:3
240
239.2 493.8
586449.64** 1.745E-11 21.1977

A Study on Measurement of Forest Soil Redox Potential 150
Continued
338.1 494.8
338.1 494.8 0
338.1 493.8
220054.81** 1.239E-10 21.1977
338 494.8
338 494.8
1
337 493.8
110638.08** 4.901E-10 21.1977
340.3 494.8
340.3 494.8 2
340.3 493.8
213906.25** 1.311E-10 21.1977
329.5 494.8
329.5 494.8 6
329.5 493.8
244926.01** 1E-10 21.1977
305.1 494.8
305.2 494.8 12
305.2 493.8
319317.24** 5.884E-11 21.1977
274.4 494.8
274.4 494.8
24
274.4 493.8
319317.24** 5.884E-11 21.1977
276.6 494.8
276.7 494.8 48
276.7 493.8
422704.51** 3.358E-11 21.1977
247.2 494.8
247.2 494.8
96
247.2 493.8
550267.24** 1.982E-11 21.1977
245.1 494.8
245.1 494.8
144
245.1 493.8
559653.61** 1.916E-11 21.1977
216.3 494.8
216.3 494.8
192
216.3 493.8
696390.25** 1.237E-11 21.1977
215.2 494.8
215.2 494.8
1:4
240
215.2 493.8
701908.84** 1.218E-11 21.1977

A Study on Measurement of Forest Soil Redox Potential 151
Continued
336.7 494.8
336.7 494.8 0
336.7 493.8
224012.89** 1.196E-10 21.1977
336.4 494.8
336.5 494.8 1
336.5 493.8
222451.49** 1.212E-10 21.1977
338.1 494.8
338.1 494.8 2
338.1 493.8
220054.81** 1.239E-10 21.1977
319.9 494.8
319.9 494.8 6
319.9 493.8
274261.69** 7.976E-11 21.1977
307.7 494.8
307.7 494.8 12
307.7 493.8
313936.09** 6.088E-11 21.1977
280.3 494.8
280.3 494.8 24
281.3 493.8
205761.13** 1.417E-10 21.1977
279.5 494.8
279.5 494.8 48
279.5 493.8
415896.01** 3.469E-11 21.1977
238.8 494.8
238.8 494.8 96
238.8 493.8
588289.00** 1.734E-11 21.1977
240.2 494.8
240.2 494.8 144
240.2 493.8
581863.84** 1.772E-11 21.1977
207 494.8
207 494.8 192
207 493.8
743733.76** 1.085E-11 21.1977
206.4 494.8
206.4 494.8
1:5
240
206.4 493.8
746841.64** 1.076E-11 21.1977
**Significance of difference is at the P < 0.01 level; *Significance of difference is at the P < 0.05 level.