Instantaneous pH Measurement
Overview: Liming efficiency.
Instantaneous pH Measurement
AIM: This GRDC project
is designed to assess the
accuracy and practicality
of using Instantaneous
pH probes to test top soil
and sub-soil pH. The
project will answer the
following questions:
Instantaneous pH Measurement
QUESTIONS:
1. How do instantaneous pH probes compare to glass
probes?
a. 1:5 CaCl2 Solution.
b. Inserted directly into soil (Direct Soil).
2. Effect of soil types.
3. Effect of soil moisture.
4. Sampling Density.
5. Can the Veris pH Detector be modified for testing at
depth?
Instantaneous pH Measurement
What is Antimony?:
• Sb pronounced “AN-the-MOH-nee”.
• Element 51 in periodic table (Metalloid)
Antimony pH probe:
• Sb pronounced “ANthe-MOH-nee”.
• 51
• Used by Egyptians as
eyeliner.
• Highly toxic.
• Amazing
Instantaneous pH Measurement
What is Antimony:
• Used by Egyptians as eyeliner.
• Brittle
• Mohs Hardness - 3
• Highly toxic.
• Has a remarkable linear
response to [H+] in solution.
• Used in medical for pH
measurement.
Instantaneous pH Measurement
QUESTIONS:
1. Glass bulb pH probes vs Antimony pH probes.
• CaCl2
Instantaneous pH Measurement
QUESTIONS:
1. Glass bulb pH probes vs Antimony pH probes.
CaCl2
pH (Glass vs Antimony) ABOVE soil in 1:5 CaCl2
6.5
y = 0.8634x + 0.3521
R² = 0.8914
6.25
6
5.75
Glass Probe
5.5
5.25
5
4.75
4.5
4.25
4
3.75
3.5
3.5
3.75
4
4.25
4.5
4.75
5
5.25
Antimony Probe
5.5
5.75
6
6.25
6.5
Instantaneous pH Measurement
QUESTIONS:
1. Glass bulb pH probes vs Antimony pH probes.
CaCl2
Antimony vs Glass Probe
6.00
y = 1.4107x - 1.8197
R² = 0.8746
pH 1:5 CaCl Glass Probe
5.50
5.00
pH (1:5) ant
4.50
4.00
3.50
3.00
3.00
3.50
4.00
4.50
pH 1:5 CaCl Antimony
5.00
5.50
Instantaneous pH Measurement
QUESTIONS:
1. Glass bulb pH probes vs Antimony pH probes.
• CaCl2
Traditional glass bulb pH
probe:
Antimony pH probe:
Instantaneous pH Measurement
QUESTIONS:
1. Glass bulb pH probes vs Antimony pH probes.
CaCl2
Direct Soil
Process.
• Map out sample sites.
• Take sample paddock
• Measure 1:5 sample for some of
those sites.
• Use 1:5 samples to scale the
Direct soil measurements
• Create pH Map.
Instantaneous pH Measurement
QUESTIONS:
1. Glass bulb pH probes vs Antimony pH probes.
Direct Soil (15sec)
Antimony (1:5 vs Direct Soil)
6.00
y = 0.9818x - 0.0123
R² = 0.716
5.50
pH Direct Soil
5.00
Detect 15s
4.50
4.00
3.50
3.00
3.00
3.50
4.00
4.50
pH 1:5 CaCl
5.00
5.50
6.00
Instantaneous pH Measurement
QUESTIONS:
1. Glass bulb pH probes vs Antimony pH probes.
Direct Soil (30sec)
6.00
Antimony (1:5 vs Direct Soil)
y = 1.025x - 0.2092
R² = 0.7315
5.50
pH Direct Soil
5.00
Detect 30s
4.50
4.00
3.50
3.00
3.00
3.50
4.00
4.50
pH 1:5 CaCl
5.00
5.50
6.00
Instantaneous pH Measurement
QUESTIONS:
1. Glass bulb pH probes vs Antimony pH probes.
Direct Soil
Comparison
R2
Glass vs Ant (1:5)
0.87
Glass vs Ant (15sec)
0.72
Glass vs Ant (30sec)
0.73
Glass vs Ant (60sec)
0.75
Glass vs Ant (120sec)
0.75
Glass vs Ant (240sec)
0.77
Instantaneous pH Measurement
QUESTION:
2. Different soil type effects.
3. Soil moisture interactions. pH = 4.12 (1:5 CaCl
Solution)
Antimony pH probe
pH Reading vs Soil Moisture %
5
4.8
4.6
4.4
4.2
4
3.8
3.6
3.4
3.2
3
2.8
2.6
2.4
2.2
2
pH
0%
2%
4%
6%
8%
10%
12%
14%
Moisture (% oven dried)
16%
18%
20%
22%
Instantaneous pH Measurement
QUESTIONS:
1. How do instantaneous pH probes compare?
a. Traditional method 1:5 CaCl2 Solution.
b. Inserted directly into soil (Direct Soil).
2. Effect of soil types.
3. Effect of soil moisture.
4. Sampling density.
5. Can the Veris pH Detector be modified for testing at
depth?
Instantaneous pH Measurement
Lime Application Map
Instantaneous pH Measurement
Lime Application Savings
Zone
Blanket
Apply
Zone
Applied
Area
(ha)
1
Total
pH
Rate (t) Lime (t)
(CaCl)
58
4.52
2
116
1
11.43
5.29
0
0.0
2
3
4
10.99
22.16
13.42
58
4.59
4.23
3.86
1
2
3
11.0
44.3
40.3
95.57
82%
1.65
Instantaneous pH Measurement
QUESTION:
Can the Veris pH Detector it be modified for testing at
depth
Instantaneous pH Measurement
Planfarm Hydraulic Soil Corer & pH Trailer:
Instantaneous pH Measurement
Planfarm Hydraulic Soil Corer & pH Trailer:
Instantaneous pH Measurement
Thank You
Instantaneous pH Measurement
Planfarm Hydraulic Soil Corer & pH Trailer:
Instantaneous pH Measurement
Planfarm Hydraulic Soil Corer & pH Trailer:
Instantaneous pH Measurement
Planfarm Hydraulic Soil Corer & pH Trailer:
Instantaneous pH Measurement
Question:
• Response Time.
Response Time - Direct Soil
6.40
6.30
6.20
6.10
pH Direct soil
6.00
y = 4E-16x6 - 9E-13x5 + 8E-10x4 - 3E-07x3 + 7E-05x2 - 0.0083x + 6.257
R² = 0.9895
5.90
pH
Poly. (pH)
5.80
5.70
5.60
5.50
5.40
0
100
200
300
400
Time (Sec)
500
600
700
800
Instantaneous pH Measurement
Questions:
1. Soil moisture.
% Moisture (Theta Probe vs Oven Dried Moisture)
16.00%
y = 0.0109x - 0.0202
R² = 0.9422
14.00%
% Moisture (Oven Dried)
12.00%
10.00%
8.00%
% Moisture (Probe)
6.00%
Linear (% Moisture (Probe))
4.00%
2.00%
0.00%
0
-2.00%
1
2
3
4
5
6
7
8
% Mositrue (Probe)
9
10
11
12
13
14