Post on 29-Mar-2023
Comparison of Soil Test Methods 2009
Comparison of Palintest Soil Analysis to External Laboratory Analysis S. Eddy and S. R. Johnston, Palintest Ltd.
This study has been carried out to provide a correlation between the test methods used in the Palintest Soil Testing Kits and recognised laboratory methods for soil analysis. Where practicable the laboratory method used the same procedure as the extraction methods recommended in the UK by MAFF/ADAS ‘The Analysis of Agricultural Materials’ Reference book 427. All samples were air dried and passed through a 2mm sieve prior to analysis. Samples batches were then split prior to testing between methods. Summary of Extraction Procedures
Test Test
Species
Palintest
Extractant
Laboratory
Extractant
MAFF/ADAS
Extractions
Nitrate N 1M Ammonium
Chloride
2M Potassium
Chloride
2M Potassium
Chloride
Phosphate P 0.5M Sodium Bicarbonate
Olsen’s Extract 0.5M Sodium Bicarbonate
Potassium K 0.1M Magnesium
Acetate Ammonium Nitrate
1M Ammonium
Nitrate
Calcium Ca 1M Potassium
Chloride Ammonium Nitrate
1M Ammonium
Nitrate
Magnesium Mg 1M Potassium
Chloride Ammonium Nitrate
1M Ammonium Nitrate
Aluminium Al 1M Potassium
Chloride EDTA Extract
No method for
Aluminium in soil
Ammonia N 1M Potassium
Chloride
2M Potassium
Chloride
2M Potassium
Chloride
Chloride Cl Water Water Saturated Calcium Sulphate Solution
Copper Cu 0.05M Disodium
EDTA Ammonium EDTA
0.05M Ammonium
EDTA
Iron Fe 1M Potassium
Chloride DTPA Extract
No method for
Iron in soil.
Manganese Mn 1M Ammonium
Chloride DTPA Extract
1M Ammonium Acetate
pH pH Lime Requirement CaCO3
No extraction required
Conductivity µS/cm Water Saturated Calcium Sulphate Solution
Saturated Calcium Sulphate Solution
Sulphate S Water Phosphate Buffer
Soluble Sulphate Water
Comparison of Soil Test Methods 2009
Results of the correlation study Aluminium
Sample Reference Palintest External Laboratory
SRJ 2.6 66.2
SWB 1.4 58.6
MSW 1.2 49.7
TKL 1.0 44.5
LRG 1.4 6.8
SLE 2.0 55.5
TAB 1.3 59.6
The Palintest aluminium results do not show any linear correlation to the external laboratory analysis this is due to the extract used to remove the aluminium from the soil. Palintest uses potassium chloride to remove the available aluminium from the soil and the tablet reagents then measure the amount of free aluminium. The external laboratory extraction method uses EDTA, which removes the extractable aluminium from the soil, and this is then determined as complexed aluminium.
Comparison of Soil Test Methods 2009
Ammonia Sample Reference Palintest External Laboratory
SRJ 6.3 1.6
SWB 45.5 47.9
MSW 10.8 12.4
TKL 16.0 16.1
LRG 28.1 25.1
SLE 19.5 19.6
TAB 3.7 0.4
Comparison of Soil Test Methods 2009
Calcium
Sample Reference Palintest External Laboratory
SRJ 2833 2500
SWB 2708 2279
MSW 2792 2339
TKL 1792 1621
LRG 2708 2355
SLE 2208 1751
TAB 2667 1956
The Calcium Tablet Count test has a detection limit of ± 250 mg/l.
Comparison of Soil Test Methods 2009
Chloride
Sample Reference Palintest External Laboratory
SRJ 67 78
SWB 63 66
MSW 59 48
TKL 59 30
LRG 42 72
SLE 46 36
TAB 59 48
The Palintest Chloride test does not show a high level of linear correlation to the external analysis. The reason it does not show a higher level of linear correlation is that the Chloride Tablet Count test has a detection limit of ± 25 mg/l. For the soil samples studied in this report the amount of chloride present and the variation between samples was insufficient to demonstrate a higher degree of correlation between the test methods. Conductivity
Sample Reference Palintest External Laboratory
SRJ 100 1965
SWB 100 1972
MSW 100 1852
TKL 100 2009
LRG 100 1959
SLE 100 1920
TAB 100 1999
The Palintest Conductivity test does not show a high level of linear correlation to the external analysis due to the extraction procedure used to remove the soluble salts from the soil. Palintest uses deionised water to remove them and the external method uses a saturated calcium sulphate solution to displace them from the soil.
Comparison of Soil Test Methods 2009
Copper
Sample Reference Palintest External Laboratory
SRJ 5.1 12.5
SWB 54.3 71.7
MSW 7.0 14.1
TKL 7.9 10.1
LRG 8.8 11.6
SLE 15.1 22.5
TAB 5.9 8.7
51023 3.8 2.7
51200 4.1 5.7
52076 8.7 10.2
52078 15.5 18.9
52359 14.0 14.5
53491 23.7 23.1
Comparison of Soil Test Methods 2009
Iron
Sample Reference Palintest External Laboratory
SRJ 41.4 40.4
SWB 44.3 27.4
MSW 51.4 82.2
TKL 50.4 41.9
LRG 19.3 42.4
SLE 37.2 26.6
TAB 51.3 77.6
51025 50.0 92.2
51201 101.6 214.4
51203 112.6 315.3
51930 108.2 404.2
53318 90.5 699.4
The Palintest Iron test does not show any linear correlation to the external analysis due to the extract used to remove the iron from the soil. Palintest uses EDTA to remove the available iron from the soil whereas the external method uses DTPA.
Comparison of Soil Test Methods 2009
Magnesium
Sample Reference Palintest External Laboratory
SRJ 151 152
SWB 220 233
MSW 123 112
TKL 240 258
LRG 109 107
SLE 228 221
TAB 302 288
248957 29 20
249344 63 48
249707 101 75
249969 175 150
249254 231 203
249128 232 255
249147 271 301
249496 401 404
Comparison of Soil Test Methods 2009
Manganese
Sample Reference Palintest External Laboratory
SRJ 0.8 2.5
SWB 20.9 19.8
MSW 7.6 3.3
TKL 8.1 4.7
LRG 4.9 2.4
SLE 11.5 5.6
TAB 5.0 4.7
51023 29.9 37.9
51025 17.1 19.3
51202 3.2 6.9
51496 22.4 24.4
51536 54.5 58.7
Comparison of Soil Test Methods 2009
Nitrate
Sample Reference Palintest External Laboratory
SRJ 55.3 58.9
SWB 16.4 26.4
MSW 40.6 36.4
TKL 14.9 14.2
LRG 10.2 7.7
SLE 13.1 11.9
TAB 31.6 35.9
Comparison of Soil Test Methods 2009
pH Block
Sample Reference Palintest External Laboratory
SRJ 6.3 6.90
SWB 6.8 6.30
MSW 7.6 7.30
TKL 7.8 7.70
LRG 7.8 8.00
SLE 6.8 7.70
TAB 7.6 6.80
249713 4.1 4.06
249890 4.7 4.50
249729 5.6 5.08
248862 5.8 5.51
248778 5.6 6.00
248917 6.8 6.50
248909 7.4 7.00
249044 7.3 7.50
248814 8.0 8.01
The pH block test has a detection limit of ± 0.5 pH units.
Comparison of Soil Test Methods 2009
pH Meter
Sample
Reference Palintest - pH Probe External Laboratory
249713 4.79 4.06
249890 5.30 4.50
249729 5.69 5.08
248862 5.76 5.51
248778 5.74 6.00
248917 6.64 6.50
248909 7.18 7.00
249044 7.71 7.50
248814 7.96 8.01
SRJ 6.92 6.90
SWB 6.36 6.30
MSW 7.31 7.30
TKL 7.60 7.70
LRG 8.05 8.00
SLE 7.87 7.70
TAB 6.91 6.80
Comparison of Soil Test Methods 2009
Phosphate
Sample Reference Palintest External Laboratory
SRJ 26 41
SWB 29 30
MSW 33 41
TKL 45 48
LRG 77 90
SLE 46 44
TAB 38 40
249017 1 5
249420 13 15
249947 20 20
249540 27 25
249790 28 35
249538 46 40
249652 35 45
248924 41 50
249557 84 80
Comparison of Soil Test Methods 2009
Potassium
Sample Reference Palintest External Laboratory
SRJ 111 92
SWB 218 157
MSW 148 152
TKL 347 377
LRG 141 156
SLE 92 56
TAB 309 330
248730 49 25
248747 77 53
248786 112 102
249190 151 151
249013 212 201
249557 204 245
249547 265 351
249576 309 400
Comparison of Soil Test Methods 2009
Sulphate
Sample Reference Palintest External Laboratory
SRJ 30.2 20.9
SWB 32.4 32.5
MSW 42.4 17.1
TKL 49.6 22.5
LRG 26.7 29.4
SLE 26.3 33.4
TAB 57.1 30.3
51023 40.0 21.2
51202 180.8 195.5
51318 96.3 56.1
51346 141.0 95.9
The extraction procedure used to remove the water soluble sulphate from the soil is different for the two methods. Palintest uses deionised water and the external method uses a phosphate buffer.
Comparison of Soil Test Methods 2009
Conclusions Overall the comparison of the results between Palintest test methods and external laboratory analysis shows a high degree of correlation, with the exception of:
• Aluminium • Chloride • Conductivity • Iron
In the cases of aluminium, conductivity and iron the variance is explained by the difference in extraction method used for these tests. In the case of chloride, no correlation can be concluded due to the small variance in concentration and degree of sensitivity of the test method at this low concentration. For aluminium and iron there are currently no recognised methods specified by MAFF/ADAS for the analysis of soils.
Test Test
Species Palintest Method
Laboratory Extractant
Correlation
Nitrate N 1M Ammonium
Chloride
2M Potassium
Chloride �
Phosphate P 0.5M Sodium
Bicarbonate Olsen’s Extract �
Potassium K 0.1M Magnesium
Acetate Ammonium Nitrate �
Calcium Ca 1M Potassium
Chloride Ammonium Nitrate �
Magnesium Mg 1M Potassium
Chloride Ammonium Nitrate �
Aluminium Al 1M Potassium
Chloride EDTA Extract
Ammonia N 1M Potassium
Chloride
2M Potassium
Chloride �
Chloride Cl Water Water
Copper Cu 0.05M Disodium
EDTA Ammonium EDTA �
Iron Fe 1M Potassium
Chloride DTPA Extract
Manganese Mn 1M Ammonium
Chloride DTPA Extract �
pH pH Lime Requirement CaCO3
No extraction required
No extraction required �
Conductivity µS/cm Water Saturated Calcium
Sulphate Solution
Sulphate S Water Phosphate Buffer Soluble Sulphate �