Asian Soil Laboratory Network: 3rd meeting. Manila, Philippines, 23 - 27 September 2019. Ms. Gina Nilo, Philippines

1. Available Phosphorus Bray II
GLOSOLAN-SOP-BRAY II/01
Gina P. Nilo, Ph.D.
Philippines

2. Common Procedures/Steps
among SEALNET member
countries

3. Particle size (mm)
Country Particle size (mm)
Cambodia <0.5 mm
India ≤ 2 mm
Japan ≤ 2 mm
Laos PDR ≤ 2 mm
Myanmar ≤ 2 mm
Nepal ≤ 2 mm
Philippines ≤ 2 mm
Thailand ≤ 2 mm
Vietnam ≤ 2 mm
Particle Size:
≤ 2 mm

4. Sample/Extractant Ratio
Country Sample weight (g) Volume of extractant
(mL)
Ratio
Cambodia 2.85 20 1 : 7.02
India 2.00 14 1 : 7
Japan 1.00 20 1 : 20
Laos PDR 2.50 25 1 : 10
Myanmar 2.00 10 1 : 5
Nepal (NARC) 2.00 20 1 : 10
Nepal (SMD) 2.85 20 1 : 7.02
Philippines 2.85 20 1 : 7.02
Thailand
(Kasetsart
Univeristy) 2.50 20 1 : 8
Thailand (LDD) 2.00 20 1 : 10
Vietnam 2.50 35 1 : 14
Sample/Extractant
ratio:
1 : 7.02

5. Shaking Time and Method
Country
Shaking Time,
min Shaking Method
Cambodia 1 Shaker
India 1 Shaker
Japan 1 Hand
Laos PDR 50 Hand
Myanmar 1 Hand
Nepal (NARC) 5 Shaker
Nepal (SMD) 1 Shaker
Philippines 1 Shaker
Thailand (Kasetsart
Univeristy) 1 Shaker
Thailand (LDD) 1 Hand
Vietnam 0.6 Hand
Shaking Time and
Method:
1 minute in Shaker
(reciprocating)

6. Filter Paper No. and Filtration Time
Country Filter Paper Filtration time, min
Cambodia No. 42 (Whatman) Not to exceed 10 minutes
India No. 42 (Whatman) Not to exceed 10 minutes
Japan No. 6 (Advantec) -
Laos PDR No. 42 (Whatman) Not to exceed 10 minutes
Myanmar No. 42 (Whatman) Not to exceed 10 minutes
Nepal (NARC) No. 42 (Whatman) 10
Nepal (SMD) No. 42 (Whatman) -
Philippines No. 42 (Whatman) Not to exceed 10 minutes
Thailand (Kasetsart
Univeristy) No. 42 (Whatman)
Not to exceed 15 minutes (up to
soil testure)
Thailand (LDD) No. 5 (Whatman) Filter until it all out
Vietnam No. 42 (Whatman) Not to exceed 10 minutes
Whatman No. 42,
Not to exceed 10
minutes

7. Mixed Reagent Composition
Country Mixed Reagent
Composition
Philippines
ASCORBIC ACID METHOD
Ammonium molybdate
Potassium antimonyl tartrate
H2SO4
Ascorbic Acid
Myanmar
India
Nepal (NARC)
Thailand (Kasetsart
Univeristy)
Thailand (LDD)
Laos
Vietnam
Japan
Nepal STANNOUS CHLORIDE METHOD
Chloromolybdic acid
Stannous Chloride stock solutionCambodia
Ascorbic Acid
Method
Note:
Preparation varies per reference

8. Standard Series
Country mg/L
Cambodia 0, 0.1, 0.2, 0.4, 0.6, 0.8, 1.0
India 0, 0.04, 0.08, 0.12, 0.16, 0.20
Japan 0, 0.4, 0.8, 1.2, 1.6, 2.0
Laos 0.1, 0.2, 0.4, 0.8, 1.2
Myanmar 0.2, 0.4, 0.6, 0.8, 1.0
Nepal (NARC) 0.2, 0.4, 0.8, 1.2
Nepal (SMD) 0, 0.04, 0.08, 0.16, 0.24, 0.32, 0.4
Philippines 0, 0.5, 1, 1.0, 1.5, 2.0, 2.5, 3.0
Thailand (Kasetsart University) 0, 0.2, 0.4, 0.6, 0.8, 1.0
Thailand (LDD) 0, 1, 2, 3, 4, 5, 6, 8, 10, 15
Vietnam 0, 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 2.0
Standard Series:
Varies per reference
ISRIC (Reeuwij, 2002) procedure
best describes the standard series

9. Volume of Standard Series, Blanks & Extracts
Country Volume of Standard
Series, mL
Volume of Method
Blank, mL
Volume of Sample
Extracts, mL
Cambodia - 5.0 5.0
India 5.0 5.0 5.0
Japan 1 – 5 5 – 15 5 – 15
Laos - 5.0 5.0
Myanmar 1.0 1.0 1.0
Nepal (NARC) 25.0? 25.0? 5.0
Nepal (SMD) 50.0? 50.0? 5.0
Philippines 3.0 3.0 3.0
Thailand
(Kasetsart
University)
- - -
Thailand (LDD) 0.5 - 0.5
Vietnam - - -
Varies per
reference

10. Volume of Boric Acid & Mixed Reagent
Country Volume of Boric
Acid, mL
Volume of the
Mixed Reagent, mL
Cambodia 7.5 7.5
India 0 4.0
Japan 20.0 8.0
Laos Didn’t use 5.0
Myanmar 1.0 8.0
Nepal (NARC) 7.5 4.0
Nepal (SMD) 15.0 10.0
Philippines 3.0 3.0
Thailand (Kasetsart
University)
- -
Thailand (LDD) - 8.0
Vietnam - -
Varies per
reference

11. Standing Time
Country Min
Cambodia At least 6 mins to develop its maximum
India At least 10 mins to develop its maximum
Japan At least 15 mins to develop its maximum
Laos At least 30 mins to develop its maximum
Myanmar 60 mins
Nepal (NARC) 10.0
Nepal (SMD)
At least 5 mins to 15 mins develop its
maximum
Philippines At least 60 mins to develop its maximum
Thailand (Kasetsart University) At least 20 mins to develop
Thailand (LDD) At least 30 mins to develop
Vietnam At least 30 mins to develop its maximum
SOP:
30 or 60minutes

12. Wavelength
Country nanometers
Cambodia 650.0
India 882.0
Japan 710.0
Laos 882.0
Myanmar 882.0
Nepal (NARC) 882.0
Nepal (SMD) 660.0
Philippines 880.0
Thailand (Kasetsart University) 880.0
Thailand (LDD) 882.0
Vietnam 882.0
SOP:
882.0 nm

13. Reference Material Used
Country Reference Material
Cambodia
India Phosphate Standard Solution (1000 mg/L), Check Sample (Internal Sample)
Japan
Laos Check Sample (Internal Sample)
Myanmar KH2PO4 solution (100 mg P/L), Check Sample (Internal Sample)
Nepal (NARC)
NIST Traceable Phosphate Standard Solution (1000 mg/L)
Local Control (Master) Sample
Nepal (SMD)
Standard Solution (AR KH2PO4 ), CRM for Soil, Check Sample (Internal
Sample)
Philippines
NIST Traceable Phosphate Standard Solution (1000 mg/L),
CRM for Soil, Check Sample (Internal Sample)
Thailand (Kasetsart
University)
Check Sample (Internal Sample)
Thailand (LDD) NIST SRM #3139a (1000 mg/mL) Phosphorus in H2O
Vietnam
NIST Traceable Phosphate Standard Solution (1000 mg/L),
CRM for Soil, Check Sample (Internal Sample)
SOP: NIST Traceable P Standard Solution, CRM, IRM

14. Quality Control Measures
Country Reference Material
Cambodia
India Duplicate analysis in every 10 samples and employing Relative
Standard Deviation, %-Method Blank-Method Detection Limit
Japan
Laos 10% duplication (2 samples are duplicate in one batch-20
samples)
Quality Control Chart
Myanmar
Nepal (NARC) 1. Setting spectrophotometer for measuring a sample in 2
times
2. Using 2 Local Control (Master Sample) in each lot of samples
3. Trying to make lab temperature 25 degree as much as
possible
4. Including 2 blank samples in each lot of measurement
Nepal (SMD) Duplicate analysis in every 10 samples and employing
Method Blank-Method Detection Limit
Philippines Duplicate analysis in every 10 samples and employing Relative
Standard Deviation, %-Method Blank-Method Detection Limit
Thailand (Kasetsart University)
Thailand (LDD) control sample (Internal Sample)
Vietnam -
1. Duplicate analysis in
every 10 samples and
employing Relative
2. Standard Deviation, %
3. Method Blank
4. Method Detection
Limit

15. Report Unit and No. of Decimal
Country Unit Number of Decimal
Cambodia ppm 2
India mg/kg 2
Japan mg P2O5/kg 2
Laos mg/kg 2
Myanmar mg/kg 1
Nepal (NARC) mg/kg 2
Nepal (SMD) P2O5 kg/ha 2
Philippines mg/kg 2
Thailand (Kasetsart University) mg/kg 2
Thailand (LDD) mg/kg Integer
Vietnam mg/kg 2
Unit:
mg/kg,
No. of Decimals:
2 decimals

16. Report base on air dry or oven dry
Country Report
Cambodia oven dry basis
India Air dry basis
Japan oven dry basis
Laos air dry basis
Myanmar oven dry basis
Nepal (NARC) oven dry basis
Nepal (SMD) air dry basis
Philippines oven dry basis
Thailand (Kasetsart University) on air dry
Thailand (LDD) base on air dry
Vietnam oven dry basis
Report Basis:
Oven Dry

17. Factors Affecting Analysis of Available P – Bray II
1. Sample particle size
2. Extraction time
3. Composition of mixed reagent

18. Effect of Particle Size, mm
• Sieving through a 10-mesh (2-mm) screen removes stones and other
extraneous substances, yielding a uniform sample that can be easily
handled in the laboratory and stored indefinitely (J.Benton Jones).
• The soil is screened through a 2-mm sieve. The practice of passing
only a portion of the ground sample through the sieve and discarding
the remainder is erroneous. This introduces a positive bias in the
sample as the rejected part may include soil elements with
differential fertility. Therefore, the entire sample should be passed
through the sieve except for concretions and pebbles of more than
2 mm (Motsara, M.R, Roy, R.N)
Conclusion: The size of the sample to be use must be uniformed.

19. Extraction Time
Extraction time is based on time necessary to reach
equilibrium. For most acid extraction reagents, equilibrium is
reach quickly, and the time of the extraction is based more on
ease of mechanical handling. For Bray I, equilibrium is reached
in 60 s or 1 min. Long periods of contact between soil and
extraction reagent, by overextending the extraction time or
delaying separation by either filtration or centrifugation,
allow P reabsorption to take place.
Source: B. Jones (2001) - Laboratory Guide for Conducting Soil Tests and Plant Analysis.

20. • The Mo-ascorbic blue methods are the most sensitive and, as a result, are widely
used for soil extract containing small amounts of P as well as for total P in soils. The
intensity of the blue color varies with the P concentration but is affected also by other
factors such as acidity, arsenates, silicates, and substances that influence the oxidation-
reduction condition of system. (R.H Miller, Methods of Soil Analysis Part 2)
• The advantages of the ascorbic acid method (Murphy & Riley, 1962) over the
stannous chloride method are the longer stability of the molybdenum blue color and
tolerance of high salt and Fe3+ (up to 2.5 mgL-1) concentrations.
• With the acid molybdate solution phosphate forms phospho-molybdenic acid which is
reduced to phospho-molybdenic with Ascorbic Acid. The antimony accelerates the
development of the blue colour and stabilizes this for up to 24 hrs. With this method
interference of Si is not expected. (ISRIC).
COMPOSITION OF MIXED REAGENT

21. Thank you for your attention.