1

INTERNSHIP REPORT

Work completed at

Soil Physics Research ProgramLAND RESOURCES RESEARCH INSTITUTE

NATIONAL AGRICULTURAL REASERCH CENTRE ISLAMABAD

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

Submitted by:

SALEEM ULLAHReg. No. 10-US-AGR-186

Roll No. BAGF10E027

2

Department of Soil & Environmental ScienceUNIVERSITY COLLEGE OF AGRICULTURE

UNIVERSITY OF SARGODHA

LIS T O F CONTENTS

Title Page i

Introduction to Soil Physics Program ii

Research Title 1

Introduction 1

Materials and Methods 3

Results and Discussion 13

Conclusion 14

Table 1 14

Table 2 15

Figure 1 16

Figure 2 17

References 18

3

CERTIFICATE

This is to certify that SALEEM ULLAH (Reg. No. 10-US AGR-186) is a student of department

of Soil science from University College of Agriculture, University Of Sargodha has successfully

completed his internship on, “Relationship of Soil Physical & Chemical Properties with

Aggregate Stability in Rice-Wheat Soil” at Soil Physics laboratory’ Land Resources Research

Institute (LRRI), National Agriculture Research Center (NARC), Islamabad.

Supervisor (s)

Supervisor at NARC: Supervisor at university

Dr. Ghulam Nabi Dr. Ghulam Sarwar

____________________ ___________________

Principal Scientific Officer Head of DepartmentLRRI /NARC University College of agriculture

University of Sargodha

4

5

Dedicate to

My parents

(Mother)

Who guided me to the right path,

Who’s kind and motivative behavior let me able to

accomplish this task.

Especially to

My uncle, Brother & sister who support me

In each step of my life.

6

ACKNOWLEDGMENT

Each and every praise is to almighty “ALLAH” The most kind and merciful, the most beneficent. Who is

entire source of knowledge and wisdom endowed to mankind and countless salutations be Holy Prophet

Muhammad (PBUH), who is forever a true torch of guidance and knowledge for humanity

It gives me great pleasure to acknowledge the consideration of Dr. Ghulam Nabi, PSO/PL,NARC

Islamabad who accepted our request and gave me an opportunity to learn under his guidance.

I would also like to thanks Mr. Shahid Maqsood Gill, PSO, NARC & Mr. Ijaz Ali, SSO, NARC and

Dr. Ghulam Sarwar Head of Department (Soil& Environmental science) who was with me right from

the start till the end and gave me latest information regarding the relevant field, shared knowledge with

me in the form of lectures or discussion which gave me the confidence to perform practical work. I totally

attribute my modest success and achievements I had during this internship to them.

I have no words to express my deepest gratitude and heartiest thanks to Mr. Ghulam Haydar (Lab

Assistant) Soil Physics.

To pen off, I’m very thankful to My parents to MALIK FAIZ ULLAH BOURANA and MALIK

NASAR ULLAH NASIR BOURANA for always being there for me when I needed them, My Soil

Physics Laboratory Internship Fellow especially Ms. Asma Tanveer and Ms. Seemab Liaqat who

shared their wisdom with me, and my fellows Mr. Adeel Ashraf, Syed Hamad Haydar, Saddam

Hussain, Malik Gul Hassan Awan,. Muhammad Tayyab and my seniors Mr Shahid Ul Qadri,

Shahbaz Ali & Osama Baloch and all friends who always wanted me to be successful and shared the

most memorable moments of my life. Their encouragement, helpfulness and support kept me going.

(SALEEM ULLAH)

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LAND RESOURCES RESEARCH INSTITUTE

NARC

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. The proceeding

pages provide an overview of its mandate, accomplishments, services offered and future thrusts.

 The Mission

Provide scientific bases for enhancing and sustaining soil productivity and protecting the environment.

 Objectives

Conduct strategic soils research to understand soil physical, chemical and biological processes.

Develop technologies for efficient soil input management and environmental protection. Provide technical support to other research organizations, educational institutions, and

relevant industry.

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INTRODUCTION

Soil aggregates are groups of soil particles that bind to each other more strongly than to adjacent

particles. Aggregate stability refers to the ability of soil aggregates to resist disintegration when

disruptive forces associated with tillage and water or wind erosion are applied. Aggregate

stability suggests how well a soil can resist raindrop impact and water erosion, while size

distribution of aggregates can be used to predict resistance to abrasion and wind erosion.

Changes in aggregate stability may serve as early indicators of recovery or degradation of soils.

Aggregate stability is an indicator of organic matter content, biological activity, and nutrient

cycling in soil. Generally, the particles in small aggregates (< 0.25 mm) are bound by older and

more stable forms of organic matter. Microbial decomposition of fresh organic matter releases

products (that are less stable) that bind small aggregates into large aggregates (> 2-5 mm). These

large aggregates are more sensitive to management effects on organic matter, serving as a better

indicator of changes in soil quality. Greater amounts of stable aggregates suggest better soil

quality. When the proportion of large to small aggregates increases, soil quality generally

increases.

Stable aggregates can also provide a large range in pore space, including small pores within and

large pores between aggregates. Pore space is essential for air and water entry into soil, and for

air, water, nutrient, and biota movement within soil. Large pores associated with large, stable

aggregates favor high infiltration rates and appropriate aeration for plant growth. Pore space also

provides zones of weakness for root growth and penetration. Surface crusts and filled pores

occur in weakly aggregated soils. Surface crusts prevent infiltration and promote erosion; filled

pores lower water-holding and air-exchange capacity and increase bulk density, diminishing the

conditions for root growth.

The size of aggregates and aggregation state can be influenced by different cropping processes

and agriculturalactivities that alter the content of organic matter and the biological activity of the

soil. Over short periods of time,the stability of soil aggregates is modified under the influence of

different cropping treatments, probably beingmore related to changes in the organic constituents

than to the actual total organic matter content .However, over long periodsof time, the stability of

the aggregates diminishes as the organic matter content declines as a result of it being usedas an

energy source by the microorganisms of the soil.

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Crop systems present a differentiated behavior on soil aggregation. Grasses, due to their

extensive root system, arethe plants that present the greatest effect on the aggregation and the

highest aggregate stability (Harris et al., 1996). On the other hand,the different crop systems

exercise their effects on the formation and stabilization of the aggregates in adifferentiated way

and that depending on the type of cropping and soil use, their effects will be bigger or smaller

interms of degradation. Considering these aspects, the objective of this work was to evaluate the

impact of croprotation and soil management systems on its structural stability, measured from

the distribution of the size of water.

The aggregation is strongly affected by physic-chemical characters of any given soil. Rice wheat

soils are intensively cultivated and are characterized of having low organic matter content. How

its aggregation is related to soil physical characters is not explored. Therefore present study was

undertaken to evaluate the relationship between physic- chemical properties of rice- wheat soil

and soil aggregation parameters.

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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.

1. Soil Reaction (pH)

The soil pH is determined to evaluate wither the soil is acidic or alkaline. It is an important soil property

since it directly affects availability of plant nutrients. The ideal pH range for a soil is from 6.5 to 7.5

because most of the nutrients are available in this range. The pH was measured in 1:2 soil to water ratio as

described by (Ryan 2001) as under:

Apparatus:

i. pH meterii. Plastic cups, Beakersiii. Distilled water

i. Soil Extraction

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. After this the contents were stirred with every 10 minutes interval.

ii. 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 were prepared

by dissolving respective buffer tablets in 100 ml

distilled water. The pH meter was standardized with

these buffer solution.

For calibration, theelectrode was dipped in buffer

solution of pH 7.0 and reading on meter displaywas

adjusted to exactly 7.0 by rotating pH meter knob.

Then pH electrode was removed from the buffer

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solution, washed with distilled water and whipped 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.

iii. 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 combinedelectrode

was removed from the suspension and rinsed with distilled water and dried with tissue paper thoroughly.

2. Electrical Conductivity

The main objective to determine the EC value is evaluate concentration of total salts present the soil. The

EC value reflectssalinity status of a soil. The Ec was measured in 1:2 soil to water ratio as described by

(Ryan 2001) detailed as under:

For 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. After this the contents were stirred with every 10 minutes

interval.

Apparatus:

iv. Conductivity meter

v. Plastic cups, Beakers

vi. Standard Potassium Chloride (KCl) Solution (0.01N)

vii. Distilled water

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.

After calibration, the suspension was stirred and electrode of EC meter was dipped deep into the

suspension and reading was taken. After taking the reading the conductivity electrode was removed from

the suspension and the cell was rinsed with distilled water and dried with tissue paper thoroughly and

stored in laboratory for future use.

O.M (%) =(ml for blank – ml for sample)

Weight of Sample ().

X0.069X 0.5

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3. Soil Organic Matter

Soil Organic matter is defined as a group of carbon containing compounds that have been originated from

living beings (plants parts, roots, macro and microorganism) and deposited on or within the earth surface.

It includes the remains of all plant and animal bodies which have fallen on earth’s surface or purposely

applied by man in any form.

The soilorganic carbon was determined according to Nelson and Sommers(1982) as described by

Ryan etal (2001) as under

Reagents:

a. Potassium Dichromate Solution (K2Cr2O7) 1.0 N

b. Concentrated Sulphuric Acid (H2SO4)

c. Orthophosphoric Acid (H3PO3)

d. Ferrous Ammonium Sulphate solution [(NH4)2 SO4. FeSO4.6H2O]

e. Diphenylamine indicator (C6H6)2NH

Procedure:

For organic matter measurements2g air dry soil having particle size <2mm was taken into 500 ml flask

and 10 ml of 1.N Potassium di Chromatesolution 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 indicatorwere added. The color of mixture appearedviolet-blue. The contents were titrated

against 0.5 M Ferrous Ammonium Sulfate solution taken in a buretteuntil color changed to bluish green.

A duplicate set of blank samples was also run in parallel. The soil organic matter was calculated as under:

Where

i. 0.069Correction Factor

ii. 0.5 Molarity of Ferrous Sulphate solution

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4. Soil CaCO3

Ca Co3 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. 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 Ca Co3

contents in the unknown sample.

5. Particle Size Distribution

The particle-size distribution of soil expresses the proportions of the various sizes of

particles which it contains. The proportions are commonly represented by the relative numbers of

particles within stated size classes, or by the relative weights of such classes. The determination

of a particle-size distribution is commonly referred to as a particle-size analysis, a term which

has a largely superseded the older and somewhat ambiguous term “mechanical analysis” (Soil

Sci. Soc. Am.,1946, 1949; Am. Soc. Testing Mater., 1959; Inst. Chem. Eng., 1947, P.114).

Particle-size distribution is one of the most stable soil characteristics, being little

modified by cultivation or other practices. Although the usefulness of particle size analysis in

practical agriculture has sometimes being questioned, its indirect benefits have been extensive. It

has been used in many countries as a basis of soil textural

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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 partsi.e dispersion

of sample and sedimentation.

(1) Dispersion

40 g of soil was taken in plastic beaker. 60mL dispersion solution of sodium

hexametaphosphatewere added. Volume was made to 200mL by adding distilled water. The

samples were left overnight. 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.

(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

en stirring was stopped. The hydrometer was also

inserted immediately 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.

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

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H= Observed hydrometer reading

The silt+clay in the suspension was calculated using the formula;

% Silt+ clay = (CHRI )−(CHRb)

ODsoil wt 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

Similarly clay in the suspension was calculated by

Clay (%) = (CHR 2 )−CHRb

OD soilwt 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)

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.

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Figure 1. The USDA Soil Textural Triangle

6. Sodium (Na) and Potassium (K)

Sodium and potassium concentration was determine in 1:2 ratio of soil water solutionby Flame

Photometer method (Ryan 2001). The determination comprised of 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

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Reagents:

Lithium chloride (LiCl) 200ppm

i. 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 theclear filtrate was received in

the bottle.

Concentration measurement:

One ml of extract was taken into a test tube and 4 ml

of distilled water was added. 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 astandard curve was drawn. The prepared soil

extract was runin the flame photometer accordingly and Na/K concentration was back calculated from the

standard curve (soil extract)

Na was Calculate by

Na=Absorbance value*Dilution*Dilution factor

6.2 Calcium and Magnesium (Ca+Mg)

Ca and Mg in the extract was determined by titration method according to Richards (1954).

An aliquot of 2 ml from extract was taken by pipet and poured 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)=mlof EDTA used x normalityof EDTA

sa mplevolumex 100

Sodium Absorption Ratio (SAR):

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SAR was calculated by following equation

SAR =Na

√Ca+Mg2

Na, K and Ca,+ Mg are in meq/l

7. Mean Weight Diameter

The method of Kemper and Rosenau (1986) wasused 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 thetopmost of a nest of four sieves of 1.00, 0.50,,0.25 and 0.125

mm mesh size and pre-soaked for 30 minin deionized water. Thereafter, the nest of sievesand its

contents were manuallyoscillated vertically in tank of waterfor 4 minutes using 4-5 cm amplitude

at the rate of 30 times per minutes. After sieving, thesoil aggregatematerials retained on each

sieve were transferred intobeakers, dried in the oven at 105◦C until steadyweight was achieved.

The percentage ratio of theaggregates in each sieve represents the water-stableaggregates (WSA)

of size classes: >1.00,1.00–0.50, 0.50–0.25 and <0.125 mm.The mean-weight diameter (MWD)

of aggregates was calculated by the equation;

MWD =ƩXiWi

whereXi is the mean diameter of the ithsieve size and Wi is the proportion of the totalaggregates

in the ith fraction. The higherthe MWD values, higher the proportion ofmacroaggregates in the

sample and thereforebetter stability.

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8. Soil Aggregate Stability

Soil aggregate stability was

determined by wet sieving

apparatus as described

byNimmo and Perkins (2002),

using a single sieve of 0.25

mm. Weight of 4.0 g of 2 mm

air-dried aggregates were

placed on the sieves of Wet

Sieving Apparatus and washed

in cans with distilled water for

3 minutes. Then these cans were replaced with cans with a dispersing solution (containing 2 g

sodium hexametaphosphate/l) and the sieving continued until only the sand particles (and root

fragments) were left on the sieves. Both sets of cans were placed in an oven and dried at 110°C.

After drying, the weight of materials of unstable and stable aggregates was determined.

Aggregate stability was calculated as by the equation

WSA = Wds/(Wds+ Wdw)

where

WSA is the index of water stable aggregates,

Wdsis the weight of aggregates dispersed in dispersing solution (g),

Wdwis the weight of aggregate dispersed in distilled water (g).

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RESULTS AND DISCUSSION

Physical and chemical characteristics of 15 soils examined are summarized in Table 1. Their

variations and ranges are large enough to depict the degree and nature of the structural stability

to the soil characters

A perusal of the data Table 1, indicated that soil pH value ranged from 7.39 to 9.46 with a

mean value of 8.15. This indicated that majority of the soils had pH values towards higher side

than neutral (pH 7) a preferred value. Similarly, the Ec ranged from 0.088 to 0.77 dSm-1 with a

mean value of 0.321dSm-1. The soil organic matter valued ranged from 0.16 to 1.08 % with a

mean value of 0.64. It is generally believed that soils of Pakistan have organic matter around 0.5

% like other regions of the world occurring in arid and semi arid areas. Our results conform these

observations.

Majority of Pakistan soils are calcareous in nature due to its parent material. In this study

CaCO3 ranged from 0 to 11.25 % with a mean value of 3.2%. The data indicated that 4 out of 15

soils were non calcareous. Sodium adsorption ratio values ranged from 0.61 to 9.57 with a mean

value of 3.71. Mean weight diameter ranged from 0.106 mm to 0.80 mm with a mean value of

0.426 and water stable aggregated ranged from 6.82 to 22.56 % with a mean value of 16.59 %.

Water stable aggregates ranged from 6.82 to 22.56 % with a mean value of 16.59 %. The soil

under study ranged from medium (loam) to fine textured (clay loam) and majority of them were

heavy textured.

The linear correlation coefficient between various soil parameters and stability indicators

examined is presented at Table 2. The data Table 2 indicated that a strong correlation existed

between soil organic matter and soil pH. Similarly a very strong positive relationship was

observed for soil organic matter and mean weight diameter as well as for water stable aggregates

as depicted in Figure 1. A negatively strong relationship existed between soil pH and mean

weight diameter as well as for water stable aggregates. A non-significant correlation was

observed between SAR and CaCO3 for mean weight diameter and water stable aggregates

(Figure 2) however a significant positive relationship existed between clay and mean weight

diameter. The lower stability with clay fraction may be due to clay type as smectite and

21

illiteclays have lower cementing properties (Kaewano et.al., 2009). A negative but strong

relationship was observed for sand and mean weight diameter (Figure 2)

CONCLUSION

Soil aggregate stability is an important property of soil since it affects sustainability and crop

production. Intensively cultivated rice–wheat soils under report depicted a wide range of

variations in pysico-chemical character and their relationship with aggregate stability parameters.

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.

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 (%)

SARMWD(mm)

WSA (%)

Sand (%)

Silt (%)

Clay (%)

Minimum 7.39 0.088 0.16 0.00 0.61 0.106 6.82 12.10 16.00 20.00

Maximum 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 39.89 115.72 76.51 50.60 29.27 43.32 34.17 24.29

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Table 2. Linear Correlation Coefficient between structure stability indicator and soil characteristics

pH

(1:2)

Ec

(1:2)

OM

(%)

MWD

(mm)WSA (%)

SARLime (%)

Clay (%)

Ec(1:2)0.437ns0.103

_ _ _ _ _ _ _

OM (%)0.0646**0.009

0.0100.972ns

_ _ _ _ _ _

MWD-0.738**0.002

-0.1030.714ns

0.949**

0.000_ _ _ _ _

WSA (%)

-0.579**0.024

-0.014

0.961ns0.531*0.042

0.579*0.024

_ _ _ _

SAR0.025 ns0.928

-0.475*0.073

0.127 ns0.651

0.173 ns0.537

-0.2430.384ns

_ _ _

Lime (%)

0.688**0.005

0.798**0.000

-0.2820.308ns

-0.3580.190ns

-0.208

0.458ns-0.446*0.096

_ _

Clay

(%)-0.0129*0.0646

0.0260.927ns

0.3930.148ns

0.465*0.080

0.4190.120ns

0.0340.905ns

0.1970.481ns

_

Silt

(%)-0.561**0.030

0.411 ns0.128

0.732**

0.0020.692**0.004

0.4330.107ns

-0.2080.457ns

-0.0070.979ns

0.1820.516ns

Sand (%)

0.05210.047ns

-0.3520.198ns

-0.755**0.001

-0.733**0.001

-0.538*0.039

0.158 ns0.573

-0.078ns0.782

-0.578*0.024

** = P-value significant at 5% probability level* = P-value significant at 10% probability levelns= non-significant

23

0.00 0.20 0.40 0.60 0.80 1.00 1.200.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

f(x) = 0.800145041395989 x − 0.0795045293546883R² = 0.900655215047508

Organic Matter (%)

Mea

n W

eigh

t Dia

met

er (m

m)

0.00 0.20 0.40 0.60 0.80 1.00 1.200

5

10

15

20

25

30

f(x) = 15.9241060180077 x + 6.44563474515747R² = 0.577940167910289

Organic matter (%)

Wat

er S

tabl

e ag

greg

ates

(%)

Figure 1. Relationship between organic matter and mean weight diameter and Water stable

aggregates

24

0.00 0.20 0.40 0.60 0.80 1.00 1.200.0

2.0

4.0

6.0

8.0

10.0

12.0

f(x) = 1.41311314565601 x + 3.01759004639313R² = 0.0162555422886347

Organic matter(%)

Sodi

um A

dsor

ptio

n R

atio

(SA

R)

0 10 20 30 40 50 60 700.00

0.20

0.40

0.60

0.80

1.00

f(x) = − 0.0108288621864918 x + 0.818849433512524R² = 0.59708711553771

Sand (%)

Mea

n w

eigh

t dia

met

er (m

m)

Figure 2. Relationship between organic matter and mean weight diameter and water stable

aggregates

25

REFERENCES

Gee, W.G. and J.W. Bauder1986.Particle size analysis. In Methods of Soil Analysis. Part 1.

Physical and Mineralogical Method (Ed. A. Klute, pp 383-411). ASA, .Madison, WI

ICARDA.

Harris, R.F., G. Chesters, and O.N. Allen,1996. Dinamics of soil aggregation. Adv. Agrom., New

York. 18, 107-169.

Kaewmano, C., I. Kheoruenromne, A. Suddhiprakarm and R.J. Gilkes. 2009. Aggregate stability

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Kemper D W and R. C.Rosenau. 1986 Aggregate stabilityand size distribution; In: Methods of

Soil Analysis,Part 1 (Ed.Klute A), Am. Soc. Agronomy, Madison,WI pp. 9425–442.

Nelson D W and Sommers L E 1982 Total carbon, organiccarbon and organic matter; In:

Methods of Soil Analysis,Part 2 (ed.) Page A L, Am. Soc. Agronomy, Madison,WI,pp.

539–579.

Nimmo, J.R. and Perkins K.S. 2002. Aggregate stability and size distribution. In Dane, J.H., and

Topp, G. C., eds;,Methods of Soil Analysis, Part 4. Physical Methods: Madison, Wi,

SSSA, p317-328.

Richards 1954. Diagnosis and Improvements in Saline and Alkalis. USDA, Handbook 60.

Ryan J., G. Estefan and A. Rashid. 2001. Soil and Plant Analysis; Laboratory Manual 2 nd Edition,

ICARDA