Relationship of Soil Physical & Chemical Properties with Aggregate Stability in Rice-Wheat Soil SALEEM BOURANA

1. October, 17, 2007 1

2. 2
Relationship of Soil Physical & Chemical Properties with
Aggregate Stability in Rice-Wheat Soil
SALEEM ULLAH
Reg No#10-US-AGR-186
Roll No # BAGF10E027

3. SUPERVISIOR
Dr S.M Shahzad

4. 4
Introduction To LAND RESOURCES RESEARCH INSTITUTE
NARC
NATIONAL AGRICULTURAL REASERCH CENTRE ISLAMABAD established in 1981.
Land Resources Research institute (LRRI), established in 1982, focuses on
producing more food and fiber on less land using fewer inputs while
protecting the environment.

5. Internship Report Presentation
Work completed at
Soil Physics Research Laboratory
LAND RESOURCES RESEARCH INSTITUTE
NATIONAL AGRICULTURAL REASERCH CENTRE ISLAMABAD
“Relationship of Soil Physical & Chemical Properties with
Aggregate Stability in Rice-Wheat Soil”

6. Introduction To Project
“Relationship of Soil Physical & Chemical Properties
with Aggregate Stability in Rice-Wheat Soil”

7. Soil aggregates are groups of soil particles that bind to each other more
strongly than to adjacent particles.
 The aggregation is strongly affected by physic-chemical
characters of any given soil.
 Therefore present study was undertaken to evaluate the
relationship between physic- chemical properties of rice- wheat
soil and soil aggregation parameters.

8. Aggregate stability depend upon soil type……..
Less aggregate stability in poor soil and more aggregate
stability in good soil.
Aggregate stability depend upon disruptive forces…..
For example Rain fall, Tillage practice etc.

9. MATERIALS AND METHODS
Soil Sample Description
Soil Physics Research Program, LRRI, NARC had collected soil
samples from the rice-wheat area district Gujranwala and
Sheikhupura after harvesting rice during 2011-2012.
 The samples had been air dried, prepared and passed
through 2mm sieve.
The prepared samples had been stored in Soil Physics
Laboratory.
The surface soil samples (0-12cm) differing in physic-chemical
character were used in the study reported here.

10. Soil Reaction (pH)
 The pH was measured in 1:2 soil to water ratio as described by (Ryan 2001)
10
as under:
Apparatus:
 pH meter
 Plastic cups, Beakers
 Distilled water

11. Soil Reaction (pH)
For pH measurement
 10g air dry soil having particle size <2mm was taken into 40 ml glass
beaker and 20 ml of distilled water was added using a graduated
dispenser.
 It was mixed well with glass rod and allowed to stand for 30 minutes.

12. pH Meter Calibration
Before pH measurement,
 pH meter was calibrated and standardized with buffer two solutions.
 The buffer solution of pH 7.0 and pH 9.2
 For calibration, the electrode was dipped in buffer solution of pH 7.0 and reading on
meter display was adjusted to exactly 7.0 by rotating pH meter knob. Then pH
electrode was removed from the buffer solution, washed with distilled water and dry
with tissue paper then pH electrode was dipped into second buffer solution of pH
9.2, when stable reading on pH meter display appeared, it was adjusted to 9.2 by
rotating pH meter knob. After adjustment the electrode was removed from the
buffer solution and calibration process was repeated 3-4 times to ensure exact
calibration.

13. Recording of the Reading
After 1 hour the suspension
was stirred and electrode of pH
meter was dipped 3cm deep into
the suspension and reading was
recorded after 30 seconds.
After taking the reading the
combined electrode was removed
from the suspension and rinsed
with distilled water and dried
with tissue paper thoroughly.

14. Electrical Conductivity
The EC was measured in 1:2 soil to water ratio as described by
(Ryan 2001) detailed as under:
For EC measurement 10g air dry soil having particle size <2mm was
taken into 40 ml glass beaker and 20 ml of distilled water was added
using a graduated dispensator.
The contents were mixed well with glass rod and allowed to stand for
30 minutes.
Apparatus:
Conductivity meter
Plastic cups, Beakers
Standard Potassium Chloride (KCl) Solution (0.01N)
Distilled water

15. EC Meter Calibration
For calibration, a portion of the standard
KCl solution was taken in the plastic cup and
electrode of conductivity meter was dipped in
it. The instrument was turned on and allowed
to settle in the standard solution for few
minutes.
Calibration knob was rotated till reading on
meter display was achieved 1.413 mS/cm.
After adjustment the conductivity electrode
was removed from the solution and calibration
process was repeated 3-4 times to ensure exact
calibration.
Once calibration was complete, the
conductivity meter was ready for use.

16. Soil Organic Matter
The soil organic carbon was determined according to Nelson and
Sommers(1982) as described by Ryan etal (2001) as under
Reagents:
Potassium Dichromate Solution (K2Cr2O7) 1.0 N
Concentrated Sulphuric Acid (H2SO4)
Orthophosphoric Acid (H3PO3)
Ferrous Ammonium Sulphate solution [(NH4)2 SO4. FeSO4.6H2O]
Diphenylamine indicator (C6H6)2NH

17. Procedure:
2g air dry soil having particle size <2mm was taken into 500 ml flask
and 10 ml of 1.N Potassium di Chromate solution was added using a 10
ml pipet and mixed well.
Then 20 ml concentrated Sulfuric Acid (H2SO4) was added by using a
dispenser and allowed to stand for 30 minutes.
After this about 200 ml of distilled water was added.
Then20 ml concentrated Orthophosphoric acid was added by using a
25 ml glass cylinder and mixture was allowed to cool.
Then 10-15 drops of Diphenylamine indicator were added.
The color of mixture appeared violet-blue. The contents were titrated
against 0.5 M Ferrous Ammonium Sulfate solution taken in a burette
until color changed to bluish green..
A duplicate set of blank samples was also run in parallel.

18. The soil organic matter was calculated as under:
O.M (%) =
(ml for blank – ml for sample)
Weight of Sample
X0.069X 0.5
Where
•0.069Correction Factor
•0.5 Molarity of Ferrous Sulphate solution

19. Soil CaCO3
CaCO3 was determined by calcimeter method.
Three gram of prepared soil was
taken into 500 ml reaction flask
and 20 ml of distilled water was
added.
Then 7 ml of 4 M HCl was taken
in a reaction vial. Reaction vial was
carefully shifted into the reaction
flask taking care no HCl in the vial
should spill out.
Then the reaction flask was
connected to the Calcimeter in
such a way that it attained
completely air tight.

20. The reaction vessel was tilted gently until HCl in the vial
leaked out and reacted with vessel contents.
The carbon dioxide (CO2) produced inside the vessel
developed pressure and pushed the water column in Calcimeter
upward.
The water column reading in the Calcimeter before and after
the chemical reaction were recorded to or work out in rise the
water column due to CO2 determine produced.
A calibration curve of known concentration of CaCo3 was
drown to calculate the CaCo3 contents in the unknown sample.

21. Particle Size Distribution
Particle size distribution of <2 mm fractions was measured by the
hydrometer method as described by Gee and Bauder (1986).
The hydrometer method measures the particle size on the
differential settling velocities within a cylinder.
The procedure consists of two parts i.e dispersion of sample and
sedimentation.

22. (1) Dispersion
 40 g of soil was taken in plastic beaker.
60mL dispersion solution of sodium hexametaphosphate were added.
Volume was made to 200mL by adding distilled water.
The samples were left overnight and next day samples were transferred
to dispersion cup.
Sufficient distilled water was added in the dispersion cup.
The dispersion was carried out by mechanical shaker for 3 minutes.

23. (2) Sedimentation
The contents of cup were transferred to 1000ml
cylinder and volume was made up to 1000 ml.
The samples were stirred with the help of plunger.
Time recoding on stop watch was started immediately
when stirring was stopped.
The hydrometer was also inserted into the cylinder to
record first hydrometer reading after 40 seconds of
stirring.
After 40 seconds 1st hydrometer reading was taken
and temperature was also noted.
The second reading was taken after 2 hours and then
correction factor was applied according to the Stock’s
law.

24. Calculations
Corrections for Temperature and density:
If temperature of the sample was higher than 20 ° C, 0.36 units were
added to every hydrometer reading of sample and 0.36 unit were
subtracted for every 1° C below 20° C.
CHR= H ±[(T ±20)*0.36]
Where
CHR= Corrected hydrometer reading
H= Observed hydrometer reading

25. The silt+clay in the suspension was calculated using the formula
% Silt+ clay = x 100
Where
CHR1 is corrected Hydrometer reading 1, (taken after 40 seconds)
CHRb is corrected hydrometer reading for blank
OD soil wt = Oven dry weight of soil used

26. Similarly clay in the suspension was calculated by
Clay (%) = x 100
Where
CHR2 is corrected Hydrometer reading 2, (taken after 2 hours)
CHRb is corrected hydrometer reading for blank
The individual quantities of silt and sand were worked out from the above data as under
Silt (%) = (silt+clay) – clay
Sand (%) = 100- (silt+clay)

27. The quantities of sand, silt and clay obtained from these calculations were plottedon
USDA Soil Textural Triangle and the corresponding soil textural classes were obtained.
The USDA Soil Textural Triangle

28. Sodium (Na) and Potassium (K)
Sodium and potassium concentration was determine in 1:2 ratio of soil
water solution by Flame Photometer method (Ryan 2001).
The determination in two steps i.e soil extraction and concentration
measurements on flame photometer
Apparatus and reagents:
Extraction flasks
Reciprocating shaker
Whatman 42 Filter paper
Storing bottle
Test tube
Flame photometer
Burretts
Reagents:
Lithium chloride (LiCl) 200ppm

29. Soil Extraction
 10g air dry soil particle size <2mm was
taken into 250 ml conical flask and 20 ml
of distilled water was added using a
graduated dispenser and were shaken
samples for 30 minutes on mechanical
shaker.
 After shaking sample were filter through
filter paper Whatman No.42 and the clear
filtrate was received in the bottle.

30. Concentration measurement:
 One ml of extract was taken into a test tube and 4 ml of distilled water was added.
30
 Then 5 ml of Lithium chloride (LiCl2) was added and stirred on vortex mixture.
 Flame photometer was operated according to the instruction provided for equipment.
 A series of standard was run ranging from 0 to 10 ppm for Na+/K separately and
standard curve was drawn.
 The prepared soil extract was run in the flame photometer accordingly and Na/K
concentration was back calculated from the standard curve (soil extract)
Na was Calculate by
Na=Absorbance value x Dilution x Dilution factor

31. 31
Calcium and Magnesium (Ca+Mg)
 Ca and Mg in the extract was determined by titration method according to
Richards (1954).
 The 2 ml from extract was taken by pipette and put into the china dish.
 Then 10 drops of buffer indicator and 2-3 drops of Ericrome black-T and
titrate against with 0.01 N EDTA then titrate until the color changes from red
to blue .
 The dark blue color was end point and note the end point.
Calculation:
Ca+Mg (me/l)= x 100

32. Sodium Absorption Ratio (SAR)
SAR was calculated by following equation
SAR =
Na, K and Ca,+ Mg are in meq/l

33. Mean Weight Diameter
 The method of Kemper (1986) was used to determine mean weight diameter.
 A nest of four sieves (1.00, 0.50,0.25 and 0.125mm) was used for MWD
determinations. 40 g of <2.0 mm air-dried soils were put in the topmost of a nest of
four sieves of 1.00, 0.50,,0.25 and 0.125 mm mesh size and pre-soaked for 30 min in
deionized water.
 The nest of sieves and its contents were manually oscillated vertically in tank of
water for 4 minutes using 4-5 cm amplitude at the rate of 30 times per minutes.
 After sieving, the soil aggregate materials retained on each sieve were transferred
into beakers, dried in the oven at 105◦C until steady weight was achieved.
 The percentage ratio of the aggregates in each sieve represents the water-stable
aggregates (WSA) of size classes: >1.00,1.00–0.50, 0.50–0.25 and <0.125 mm.

34. The mean-weight diameter (MWD) of aggregates was
calculated by the equation;
MWD =ƩXiWi
Where
Xi is the mean diameter of the ith sieve size and Wi is the
proportion of the total aggregates in the ith fraction.

35. 35
Table 1. Minimum, maximum, mean and coefficient of
variation in measured parameter of 15 examined Soil
pH
(1:2)
EC
(1:2)
d
Sm-1
OM
(%)
Lime
(%)
SAR MWD
(mm)
WSA
(%)
Sand
(%)
Silt
(%)
Clay
(%)
Mini
mum
7.39 0.088 0.16 0.00 0.61 0.106 6.82 12.10 16.00 20.00
Maxi
mum
9.46 0.77 1.08 11.25 9.57 0.800 22.56 64.00 59.80 38.10
Mean 8.15 0.321 0.64 3.20 3.71 0.426 16.59 35.54 37.38 27.08
CV
(%)
7.10 58.24 39.89 115.7 76.51 50.60 29.27 43.32 34.17 24.29

36. Table 2. Linear Correlation Coefficient between structure
stability indicator and soil characteristics
pH
(1:2)
EC
(1:2)
OM
(%)
MWD
(mm)
WSA
(%)
SAR Lime
(%)
Clay
(%)
Ec
(1:2)
0.437
0.103
ns
_ _ _ _ _ _ _
OM (%) 0.0646
0.009
**
0.010
0.972
ns
_ _ _ _ _ _
MWD -0.738
0.002
**
-0.103
0.714
ns
0.949
0.000
**
_ _ _ _ _
WSA
(%)
-0.579
0.024
**
-0.014
0.961
ns
0.531
0.042
*
0.579
0.024
*
_ _ _ _

37. Conti…….Table 2.
Linear Correlation Coefficient between structure stability
indicator and soil characteristics pH
(1:2)
EC
(1:2)
OM
(%)
MWD
(mm)
WSA
(%)
SAR Lime
(%)
Clay
(%)
SAR 0.025
0.928ns
-0.475*
0.073
0.127
0.651ns
0.173
0.537ns
-0.243
0.384ns
_ _ _
Lime 0.688**
0.005
0.798**
0.000
-0.282
0.308ns
-0.358
0.190ns
-0.208
0.458ns
-0.446*
0.096
_ _
Clay 0.0129*
0.646
0.026
0.927ns
0.393
0.148ns
0.465*
0.080
0.419
0.120ns
0.034
0.905ns
0.197
0.481ns
_
Silt -0.561**
0.030
0.411
0.128ns
0.732**
0.002
0.692**
0.004
0.433
0.107ns
-0.208
0.457ns
-0.007
0.979ns
0.182
0.517ns
Sand 0.0521
0.047ns
-0.352
0.198ns
-0.755**
0.001
-0.733**
0.001
-0.538*
0.039
0.158
0.573ns
-0.078
0.782ns
-0.578*
0.024
** =P-value Significant at 5 % Probability level
*= P-value Significant at 10% Probability level
ns = non-significant

38. Relationship between organic matter and mean weight diameter

39. Relationship between organic matter and Water stable aggregates
October, 17, 2007 39

40. Relationship between sand and mean weight diameter
October, 17, 2007 40

41. Relationship between organic matter and Sodium Adsorption Ratio

42. CONCLUSION
 Soil aggregate stability is an important property of soil since it
affects sustainability and crop production.
 Based upon the results it can be concluded that stability
parameters are strongly related to soil organic matter status of
soil as well as soil texture.
 Maintaining of high organic matter levels is essential to
improve higher aggregation.