This document summarizes the key points from a presentation on soil structure and stability. It discusses how organic matter sources like municipal waste compost, farm yard manure, and poultry litter differ in their carbonaceous composition and how this affects aggregate formation and stability. The presentation hypothesized that equivalent doses of organic manures will enhance aggregate stability differently depending on their humic substance contents. Two studies found that municipal waste compost, with the highest humic acid content, most significantly increased aggregate stability and hydraulic conductivity. Maintaining good soil structure through appropriate organic amendments can improve soil quality and crop yields.

1. Presented
by
Dr. Kashif Bashir

2.  Introduction to Soil Structure & its Stability
 Highlights of Ph. D. Thesis
 Rationale, Hypothesis & Objectives
 Methodology
 Major Results & Findings
 Conclusion
 Future Research Plan

3.  The development of soil structure affects soil productivity.
 Structurally well developed soils show better hydraulic
conductivity rates and aeration within the soil system.
 The basic unit of soil structure is a soil aggregate.
 The formation and stability of various aggregate size classes are
influenced by
 Amount &
 Composition of applied organic materials
 Interaction between organic and inorganic soil components
 The different components or pools of organic carbon affect the
process of aggregate formation and stability
 Polysaccharides
 Microbial biomass carbon
 Humic Carbon and
 Fulvic Carbon

4.  INFORMATION GAP
“Whether stability of aggregate size classes vary with the
carbonaceous composition of applied organic sources”
 HYPOTHESIS
“An equivalent dose of organic manures will enhance aggregate
stability differently considering organic sources vary in contents
of humic substances”
 OBJECTIVES
 To determine carbonaceous composition in local organic matter
sources over a period of time under controlled conditions
 To develop relation between the organic source and stable aggregate
size, and
 To evaluate the hydraulic conductivity, organic carbon and wheat
yield differences due to organic amendments applied on equivalent
dose basis.

5. Study I: Organic materials characterization on the basis of
humic and non-humic substances
(1) Municipal Solid Waste Compost (2) Farm yard manure (3) Poultry litter
Incubated at 30 ± 5°C, sampled at 30 days interval, and analyzed for
 Total organic carbon (Walkley and Black., 1947)
 Total polysaccharides (Dubois et al., 1956)
 Microbial biomass carbon (Vance et al., 1987)
 Extraction of humic and fulvic acid (Swift, 1996).
Variance in the parameters were analyzed taking manure sources and time
(days) as factors (Steel et al., 1997).
Study II: Equivalent organic carbon dosages through
different amendments’ effect on selected physical
properties of soil and wheat yield.
The four rates (Control, 0.25, 0.50 and 1.0 % SOC ) of each organic amendment
(MSW Compost (MSWC), Farm Yard Manure (FYM), Poultry Litter (PL) ) were
applied on wheat crop (Chakwal 52) for two years (2012 and 2013) at two
locations (AAUR and KOONT).

6. Samples were collected at the harvesting of each year and analyzed for
 Total organic carbon (Walkley and Black, 1947)
 Saturated Hydraulic conductivity (Youngs, 1991)
 Aggregate size distribution (Chepil, 1962)
 Aggregate Stability (Kemper and Koch, 1966)
 Mean Weight Diameter (MWD) of the aggregates and aggregated (silt +
clay)
n = the number of size fractions, di = the mean diameter of each size range
wi = the weight of aggregates in that size range
 Aggregate associated carbon (Walkley and Black, 1947).
 Crop growth was assessed by biomass yield and grain yield (t ha-1).
Factorial ANOVA was used to analyze the results, and then means were
separated by LSD test at 5% level of significance (Steel et al., 1997).

7. Study I: Organic materials characterization on the basis of`
humic and non-humic substances
0
5
10
15
20
Totalorganiccarbon
(%)
Farm Yard Manure MSW Compost Poultry Litter
2.5
3.0
3.5
4.0
4.5
5.0
0 30 60 90 120 150 180
logmicC
0
7
14
21
28
35
HumicAcid(gKg-1)
0
7
14
21
28
35
0 30 60 90 120 150 180
FulvicAcid(gKg-1)
Incubation time (days)

8. Variation of dry aggregates & MWDdry with manures and their levels
Aggregate Size Ranges (mm)
Source of
Variation
4 - 8 2 - 4 1 - 2 0.5 - 1 0.25 - 0.5 0.05 - 0.25 MWDdry
Manures (g 100g-1) mm
MSW compost 10.9c 9.9b 9.5a 9.3a 19.9a 19.0a 1.26 b
Farm yard manure 12.0b 10.7a 9.8a 9.2a 19.4a 16.9b 1.35 a
Poultry litter 12.9a 10.9a 9.8a 9.1a 16.7b 15.1c 1.4 a
Levels
Control 11.8ab 10.9a 9.9a 9.4a 17.8b 17.9a 1.39 a
0.25 % SOC 11.2b 10.0b 9.8a 9.6a 19.8a 17.9a 1.23 b
0.50 % SOC 12.3a 10.3b 9.1b 8.7b 19.1ab 16.3b 1.32 ab
1.0 % SOC 12.5a 10.9a 10.1a 9.2ab 18.0b 15.9b 1.40 a
Aggregate fraction 11.9c 10.4d 9.7e 9.2f 18.9a 16.8b

9. Variation of wet stable aggregates & MWDwet with manures and their
levels
Aggregate Size Ranges (mm)
Source of
Variation
4 - 8 2 - 4 1 - 2 0.5 - 1
0.25 -
0.5
0.05 -
0.25
MWDwet
Manures ---------------------- g 100g-1 --------------------- mm
MSW compost 30.1 a 22.1 a 19.4 b 40.8 a 49.1 b 66.6 a 3.3 a
Farm yard
manure
27.9 a 22.6 a 18.9 b 41.5 a 48.6 b 63.6 b 3.2 a
Poultry litter 27.8 a 14.6 b 26.3 a 42.1 a 51.4 a 54.3 c 3.1 a
Levels
Control 21.4 b 9.9 c 15.7 c 41.1 b 46.9 c 56.6 c 2.4 c
0.25 % SOC 29.0 a 22.0 b 21.1 b 38.4 c 49.1 b 61.3 b 3.3 b
0.50 % SOC 31.9 a 25.8 a 28.1 a 42.1 ab 47.8 bc 66.5 a 3.7 a
1.0 % SOC 32.1 a 21.3 b 21.4 b 44.2 a 54.9 a 61.6 b 3.5 ab
Aggregate
fractions
30.0 d 21.8 e 22.8 e 41.6 c 50.3 b 62.5 a

10. Aggregate Size Ranges (mm)
Source of Variation 4 - 8 2 - 4 1 - 2 0.5 - 1 0.25 - 0.5 0.05 - 0.25
Manures ----------------------- g kg-1 -------------------
MSW compost 8.04 b 10.4 b 7.48 b 17.46 a 13.13 c 20.90 a
Farm yard manure 8.31 a 10.9 a 7.55 b 11.57 c 13.61 b 19.53 b
Poultry litter 7.96 b 8.51 c 8.53 a 13.43 b 14.89 a 17.11 c
Levels
Control 3.02 c 4.23 d 4.55 d 7.36 c 11.75 c 16.21 c
0.25 % SOC 9.55 b 11.9 b 8.61 b 15.61 b 14.21 b 19.47 b
0.50 % SOC 10.4 a 14.2 a 10.6 a 16.91 a 14.04 b 21.61 a
1.0 % SOC 9.46 b 9.38 c 7.64 c 16.74 a 15.51 a 19.42 b
Aggregate fractions 9.12 e 11.07 d 8.51 f 15.51 b 14.30 c 19.77 a

11. r = 0.86
0
5
10
15
20
25
0 2 4 6 8
Aggregateassociatedcarbon(gkg-1)
Mean weight diameter of wet aggregates (mm)

12. Source of Variation
TOC*
g Kg-1
Kfs**
mm hr-1
Biomass Yield
t ha-1
Grain yield
t ha-1
Manures
MSW compost 5.75 a 51.24 a 2.73 b 2.96 b
Farm yard manure 5.65 a 33.04 b 2.83 a 3.05 a
Poultry litter 5.29 a 32.11 b 2.85 a 3.06 a
Dosages
Control 4.28 b 47.88 a 2.50 c 2.63 c
0.25 % SOC 5.80 a 39.95 b 2.84 b 3.09 b
0.50 % SOC 6.29 a 34.30 bc 2.89 ab 3.16 ab
1.0 % SOC 5.89 a 33.06 c 2.97 a 3.21 a
•TOC, Total Organic Carbon
•** Kfs, Saturated Hydraulic Conductivity

13. 13
r = 0.36
0
20
40
60
80
100
120
140
160
0 2 4 6 8
Fieldsaturatedhydraulic
conductivity(mmh-1)
Mean weight diameter of wet aggregates (mm)

14.  The organic sources differ in humic and non-humic composition as
 Poultry litter had higher concentrations of microbial biomass
carbon and polysaccharide contents (active carbon pools), and
 MSW compost had highest content of humic acid (passive
carbon).
 Aggregate formation and stability of different aggregate size fractions
improved with the different sources of carbon.
 Soil structural stability is dependent on the composition of organic
sources particularly humic acid content.
 MSW compost stabilized the soil aggregates significantly due to its
highest humic acid content, which resulted into increased hydraulic
conductivity rates in the soil.

15. Tentative Logic Framework
Aim Clean Cities & Healthy Soils
Outcomes Standardized Compost for Structurally Degraded Soils
Output Most Suitable Materials for Composting Process
Research
Activities
 Collection & Characterization of the waste materials from urban
area on the basis of carbon fractions
 Screening of those materials having highest carbon
concentration
 Determination of varying levels of different Carbon fractions &
heavy metals in the screened materials during decomposition
process over 1 year incubation period
 Pre-selection of those materials having highest contents of
humic substances & least contents of heavy metals
 Evaluation of pre-selected materials on different textured un-
structured / ground soils for two years
 Selection of those materials which may improve the soil
structure and most persistent during the experimental period