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SIMULATION OF SOIL PROPERTIES AND CROP YIELD UNDER
CONVENTIONAL AND CONSERVATION TILLAGE IN
DRYLAND POTHWAR
MUHAMMAD SHARIF
10-arid-1973
Department of Soil Science & Soil and Water Conservation
Faculty of Crop and Food Sciences
Pir Mehr Ali Shah
Arid Agriculture University Rawalpindi
2
Pakistan
2015
SIMULATION OF SOIL PROPERTIES AND CROP YIELD UNDER
CONVENTIONAL AND CONSERVATION TILLAGE IN
DRYLAND POTHWAR
by
MUHAMMAD SHARIF
(10-arid-1973)
A thesis submitted in partial fulfillment of the requirement for
the degree of
Doctor of Philosophy
in
Soil Science
3
Department of Soil Science & Soil and Water
Conservation
Faculty of Crop and Food Sciences
Pir Mehr Ali Shah
Arid Agriculture University Rawalpindi
Pakistan
2015
CERTIFICATION
I hereby undertake that this research is an original one and no part of this
thesis falls under plagiarism. If found otherwise, at any stage, I will be responsible
for the consequences.
Student Name: Muhammad Sharif Signature: ______________
Registration No: 10-arid-1973 Date: _________________
Certified that the contents and form of thesis titled “Simulation
of Soil Properties and Crop Yield under Conventional and
Conservation Tillage in Dryland Pothwar.” submitted by Mr.
Muhammad Sharif have been found
satisfactory for the requirement of the degree.
Supervisor: ______________________
(Dr. Shahzada Sohail Ijaz)
Member: _________________________
(Prof. Dr. Safdar Ali)
Member: _________________________
(Dr. Muhammad Ansar)
4
Member: _________________________
(Dr. Sohail Asgher)
Chairperson: ________________
Dean: ______________________
Director Advanced Studies: _______________________
“IN THE NAME OF ALLAH, THE MOST BENEFICIENT, THE MOST
MERCIFUL”
5
DEDICATION
To
My father (late) Allah Bakhsh, may Allah bless his soul
6
CONTENTS Page
List of Tables ix
List of Figures xi
Abbreviation xii
Acknowledgement xiii
ABSTRACT 1
1 INTRODUCTION 3
2 REVIEW OF LITERATURE 9
2.1 TILLAGE AND CROP RESIDUES EFFECT ON SOIL CHEMICAL 9
PROPERTIES
2.2 TILLAGE AND CROP RESIDUES EFFECT ON SOIL PHYSICAL 16
ENVIRONMENT
2.3 TILLAGE AND CROP RESIDUES EFFECT ON CROP PRODUCTION 21
AND ECONOMICS
2.4 SOIL PROPERTIES AND CROP YIELD SIMULATION WITH 27
CENTURY MODEL
3 MATERIALS AND METHODS 31
3.1 SITE DESCRIPTION 31
3.2 TREATMENTS DETAILS 31
7
3.3 SOIL SAMPLING 32
3.4 SOIL CHEMICAL ANALYSES 33
3.4.1 Total Organic Carbon 33
3.4.2 Microbial Biomass Carbon 34
3.4.3 Particulate Organic Carbon 34
3.4.4 Mineral Associated Organic Carbon 35
3.5 SOIL FERTILITY EVALUATION 35
3.6 SOIL PHYSICAL ANALYSES 36
3.7 CROP PARAMETER 39
3.8 ECONOMIC ANALYSIS 40
3.9 PARAMETERIZATION AND VALIDATION OF CENTURY MODEL 40
3.10 METROLOGICAL DATA 44
3.11 STATISTICAL ANALYSIS 44
4 RESULTS AND DISCUSSION 46
4.1 SOIL ORGANIC CARBON AND ITS POOLS 46
4.1.1 Total Organic Carbon 46
4.1.2 Microbial Biomass Carbon 46
4.1.3 Particulate Organic Carbon 48
4.1.4 Mineral Associated Organic Carbon 50
4.2 SOIL FERTILITY STATUS 53
4.2.1 Soil Nitrate- Nitrogen 53
4.2.2 Available Phosphorus 55
4.2.3 Extractable Potassium 55
4.3 SOIL PHYSICAL PROPERTIES 58
4.3.1 Soil Structural Stability 58
4.3.2 Surface Cover 60
8
4.3.3 Soil Bulk density 60
4.3.4 Water Infiltration Rate 63
4.3.5 Total Profile Soil Water Cotents 65
4.3.6 Soil Temperature 68
4.4 WHEAT YIELD AND ECONOMICS 70
4.4.1 Seedling Emergence 70
4.4.2 Crop Biomass 72
4.4.3 Grain Yield 74
4.4.4 Harvest Index 76
4.4.5 Gross margin and efficiency coefficient 78
4.5 CENTURY MODEL VALIDATION AND SIMULATIONS 81
4.5.1 Total Organic Carbon 81
4.5.2 Microbial Biomass Carbon 84
4.5.3 Particulate Organic Carbon 88
4.5.4 Mineral associated Organic Carbon 91
4.5.5 Crop Biomass 94
4.5.6 Grain Yield 95
SUMMARY 101
LITERATURE CITED 104
APPENDICES 131 List of Tables Table No. Page
1 Physico-chemical properties of experimental soil 37
2 Detail of inputs and outputs used for economic analyses 41
3 Blocks of schedule files 43
4 Tillage and crop residues effect on soil temperature 69
9
`
List of Figures
Figure No. Page
1 Metrological scenario during the experimental period 45
2 Total organic carbon concentration under tillage and crop residue
47
3 Microbail biomass carbon under tillage and crop residues 49
4 Particulate organic carbon under tillage and crop residues 51
10
5 Mineral associated carbon under tillage and crop residues 52
6 Nitrate-nitrogen concentration under tillage and residues 54
7 Available phosphorus concentration under tillage and crop residues
56
8 Extractable potassium concentration under tillage and crop residues 57
9 Soil structural stability under tillage and residues managment 59
10 Soil surface cover under tillage systems and residues management 61
11 Soil bulk density under tillage and crop residues management. 62
12 Soil water infiltration under tillage and crop residues management 64
13 Volumetric soil water contents (2012-13) under tillage and residues
66
14 Volumetric soil water contents (2013-14) under tillage and residues 67
15 Seedling emergence under tillage and crop residues management
71
16 Wheat crop biomass under tillage and crop residues management 73
17 Wheat grain yield under tillage and crop residues management 75
18 Wheat crop harvest index under tillage and crop residues 77
19 Wheat crop gross margins under tillage systems and crop residues
79
20 Wheat crop efficiency co-efficient under tillage and crop residues 80
21 Relationship between simulated and observed soil organic carbon
82
22 Simulated total soil organic carbon under tillage and residues 83
23 Relationship between simulated and observed microbial biomass C
86
11
24 Simulated microbial biomass carbon under tillage and crop residues
87
25 Relationship between simulated and observed particulate organic C
89
26 Simulated particulate organic carbon under tillage and crop residues 90
27 Relationship between simulated and observed mineral associated C
92
28 Simulated mineral associated carbon under tillage and crop residues
93
29 Relationship between simulated and observed wheat crop biomass
96
30 Simulated wheat crop biomass under tillage and residues 97
31 Relationship between simulated and observed wheat crop yield 99
32 Simulated wheat grain yield under tillage residues management 100 LIST
OF ABBREVIATIONS
AS Aggregate Stability
CT Conventional Tillage
BD Bulk Density
EC Electrical Conductivity
GM Gross Margin
HI Harvest Index
MBC Microbial Biomass Carbon
MOC Mineral Associated Organic Carbon
MT Minimum Tillage
POC Particulate Organic Carbon
RT Reduced Tillage
+R Residues Retained
12
-R Residues Removed
SWC Soil Water Content
TOC Total Organic Carbon
ZT
Zero Tillage
ACKNOWLEDGEMENTS
I wish my humblest thanks to the ALMIGHTY ALLAH who blessed me
potential for the successful completion of this imperative task. My special praise to
the Holy Prophet Muhammad (Peace be upon him) who is a perfect model for the
whole mankind.
I would like to express my sincerest gratitude to my worthy supervisor, Dr.
Shahzada Sohail Ijaz, Assistant Professor, Department of Soil Science & SWC for their
encouraging behavior, kind cooperation, valuable suggestions and constructive
criticism during this work.
I am extremely grateful to the members of my supervisory committee Prof.
Dr. Safder Ali, Dean Faculty of Crop and Food Sciences and Dr. Muhammad Ansar
Associate Professor, Department of Agronomy for their dexterous guidance and
valuable suggestions for successful accomplishment of this research work.
13
I am thank full to Prof. Dr. Khalid Saifullah Khan , Chairman and all teaching
staff of the Department of Soil Science and SWC for their kind help and cooperation. I
highly admired all my friends for their support and help.
I also acknowledge Higher Education Commission of Pakistan for financial supports
under indigenous PhD fellowship program. I am also thankful to Government of
Balochistan for providing study leave to complete the education.
I have no words for express my father who helped me financially as well as
morally to achieve this leap of life but oh! Who has not seen me in this stage. The
patience and support provided by my mother, brothers, kids, wife and sisters during
completion of Ph.D program will always be remembered by me.
(MUHAMMAD
SHARIF)
14
ABSTRACT
Soil degradation and increasing cost of inputs are serious challenges for crop
production in dryland Pothwar, Pakistan. Conservation tillage is advocated
worldwide to improve soil properties and reduce input costs for sustainable dryland
crop production; however their effects on soil properties depend on site, climate and
length of use. Computer based models are robust tools to estimate long-term changes
in soil properties under different crop and soil management scenarios. Among these,
CENTURY model is widely used to simulate soil organic carbon (SOC) and crop
production, however literature on the performance of conservation tillage and
CENTURY model under agro-climatic conditions of dryland Pothwar, Pakistan is
scarce. Therefore, a two-year field study was carried out at University Research
Farm, Chakwal Road, of PMAS-Arid Agriculture University Rawalpindi. The
objectives were i) to compare traditional and alternative tillage practices for their
effects on biochemical and physical properties of soil ii) to evaluate conservation
tillage system against conventional practices for wheat yield and economic benefit
iii) to validate CENTURY agro ecosystem model for long term simulation of
different soil management practices under agro-climatic conditions of Pothwar.
Treatments were applied in split-plot design keeping tillage practices in main-plots
while residue management in sub-plots. The tillage treatments were a) conventional
tillage (CT), moldboard ploughed at monsoon start and cross cultivation after each
rainfall, b) minimum tillage (MT), moldboard ploughed at start of monsoon and two
cross cultivations during fallow, c) reduced tillage (RT), chisel ploughed at monsoon
start, weed controlled by chemical and wheat sown with zero drill, d) zero tillage
(ZT), no tillage applied during fallow and summer weeds were controlled through
1
15
chemical herbicide and wheat sown with zero drill. Sub-plot treatments were residue
retained (+R) and removed (-R). During winter season, wheat crop was grown in all
plots. The SOC stock and its fractions were significantly improved by ZT and RT
with retention of crop residues. The values for MBC, POC, SOC were 0.95 Mg ha-1,
4.54 Mg ha-1 and 15.84 Mg ha-1 under ZT and 0.81 Mg ha-1, 4.08 Mg ha-1and 14.21
Mg ha-1 under RT. Similarly ZT and RT with residue had 37% and 34% higher water
stable aggregates than CT without crop residue retention. As regards soil physical
properties, CT and RT reduced the bulk density, enhanced infiltration and profile
water content compared with ZT. The seedling emergence, biomass yield and grain
yield were similar under CT, MT and RT whereas ZT had lower seedling emergence
and yields. The gross margins with crop residues were the highest under RT (Rs.
109375) followed by MT (Rs. 101800) and CT (Rs. 97840), whereas ZT without
residue gave the lowest gross margin of Rs. 7187. The efficiency coefficient was the
highest under ZT (4.13) and RT (4.24). The model results strongly correlated with
actual results with the r2 values of 0.94 for TOC, 0.91 for MBC, 0.84 for POC and
0.85 for MOC. Similarly r2 values for biomass and grain yields were 0.81 and 0.76
respectively. Long-term simulations predicted that SOC can gradually increase under
all tillage systems with crop residue whereas CT without crop residue can drastically
reduce the SOC especially the MOC fraction. The simulations also showed that yield
and crop biomass can increase by residue retention in all tillage systems. The study
concludes that conservation tillage especially the reduced tillage (chiseling) and
retention of crop residues have potential to improve soil health and economic
benefits while providing sufficient yield in dryland Pothwar, Pakistan.
16
Chapter 1
INTRODUCTION
Pothwar is a semi-arid rainfed tract situated in the northern Punjab, Pakistan
(32° 10’ to 34° 9’ N and 71° 10’ to 73° 55’ E). The average minimum and maximum
temperature of the area in summer season is 15 - 40 °C while during winter is 4 - 25
°C with bimodal and erratic rainfall. About 70% annual rainfall is received during
monsoon (July-September) in the form of torrential storms while remaining rain is
received in winter as gentle shower. Two most important cropping seasons is winter
(rabi) and summer (kharif) with different cropping patterns. In (rabi) wheat
(Triticum aestivum) and gram (Cicer arietinum) and in (kharif) millet (Pennisetum
americanum), sorghum (Sorghum bicolor), maize (Zea mays) and pulses are most
widely grown. The most common soil orders of the area are Aridisols and Inceptisols
with silty loam to sandy loam texture, uneven and sloppy terrains (Nizami et al.,
2004).
Problems of soil of the area include soil erosion, desertification, land
degradation, structural instability and surface crusting (Zia et al., 2004; Rafiq, 1990).
Soil water conservation in soil profile is the major challenge (Campbell and Akhter,
1990) due to higher evaporation than precipitation. Commonly a hardpan is observed
beneath the soil surface due to intensive tillage and continuous plowing at same
depth, which restricts the movement of soil water and plant nutrients in the deeper
profile layers. The plow-pan also decreases water infiltration and thus encourages
runoff losses (Razzaq et al., 1989).
3
17
One of the major reasons for the above cited problems is low organic matter
content. The loss of organic matter in these areas is very fast due to high temperature
in summer, over grazing, clean cultivation and intensive tillage with moldboard
plow. Further the low cropping intensity and lesser biomass of crops due to water
stress, inadequate availability of essential nutrients and weed infestation ultimately
result in lesser return of organic matter to soil. These anthropogenic and natural
factors not only degrade the quality of soil but also contribute to CO2 emissions and
thus the climate changes (Bayer et al., 2006). The increasing cost of fuel and other
farm inputs are also the critical issues for resource poor farmers. All the above cited
problems ultimately affect crop production and due to that, potential yields are very
low in dryland areas of Pakistan.
Conventionally farmers of the area use moldboard plow followed by 8-10
times tine cultivator for in-situ moisture conservation and weed control. Such
intensive tillage systems encourage systematic reduction of soil organic matter,
greater susceptibility to soil erosion and sub-surface hard pan formation (Birkas,
2008). Significant CO2 emissions exhausted from the combustion of large amounts
of fuel consumed in the intensive tillage are also environmental concern (Filipovic et
al., 2006). As a result of worldwide recognition of huge problems associated with
moldboard plow, now it is the need of time to explore alternative systems which not
only sustain the quality of soil but also provide sufficient yield by reducing input cost
of farmers and help mitigate climate change by carbon sequestration.
Conservation tillage practices as an alternative to intensive tillage involve
minimum disruption to soil while leaving at least 30% of crop residues subsequent to
18
planting on the soil surface. The term includes zero tillage, minimum tillage, direct
drilling etc under its umbrella (CTIC, 2006). There are numerous benefits of
conservation tillage for soil health, water conservation, crop production and recently
accentuated environment. It increases and retains organic carbon in soil
(Franzluebbers, 2002a; Zibilske et al., 2002), improves soil water infiltration,
decreases soil surface loss through surface cover and improves soil water and
nutrient conservation (Franzluebbers, 2002b). The conservation tillage also makes
the soil stable against the deterioration by water and wind erosion (Madari et al.,
2005; Chan et al., 2002). In conservation tillage systems addition of crop residues
plays a vital role (Loveland and Webb, 2003) in altering soil chemical, physical and
biological properties (Dexter, 2004). The crop residues on the soil surface also
protect the soil from the impact of rain drop and slow down the intensity of runoff by
acting as surface barrier (Franzluebbers, 2002b; Zhao et al., 2007) thus increasing
intake of water into soil profile and in situ moisture conservation (Shaver et al.,
2002).
Soil organic carbon (SOC) is crucial and one of the essential indicators of soil
quality and sustainability (Reeves, 1997). Soil organic carbon dynamics can
astonishingly affect soil fertility and crop production in agricultural ecosystems. Soil
organic carbon is one of the most vital properties of arable land and is known as
fundamental indicator of soil quality and functions (Brown and Ulgiati, 1999;
Wardle et al., 2004). Soil organic carbon has particular effects on soil physical,
thermal, chemical and biological properties with different actions. Soil quality
always gets better by an enhanced SOC content through applications of organic
19
amendments that improves soil aggregation and have stabilization effects on the soil
structure. In addition, SOC has imperative effects on soil fertility, availability of
plant nutrient and cation exchange capacity of soil. Usually there is obvious
association between soil organic carbon contents on the soil surface and crops yield.
Crop residues in the upper surface increase organic matter content (Moreno et
al., 2006) and slow down decomposition process in subsurface due to less
availability of oxygen. Long term conservation tillage by direct drilling and leaving
stubbles on soil surface improve organic carbon in soil (Chen et al., 2009). Increase
of organic matter due to addition of residues improves soil properties (Loveland and
Webb, 2003) such soil aggregation and aggregate stability (Madari et al., 2005).
Conservation tillage also increases earthworm population and nutrient availability
(Baker et al., 2007). In short, conservation tillage system with presence of crop
residues on soil surface interfaces all soil ecology (Huang et al., 2008).
Conservation tillage system not only improves the quality of soil but also
saves time, fuel cost and sufficiently increase crop yield. Different researchers have
reported that crop yield significantly increases under conservation tillage (Hemmat
and Eskandari, 2006; Huang et al., 2008). Furthermore conservation tillage has been
found to be economically better due to reduced input costs of fuel, labor, fertilizer
and unnecessary plowing. The benefits of conservation tillage are usually expected to
appear after their long term use. It is not easy to conduct long-term experiment due to
economic constrains and perseverance.
Computer based models are robust and cheap decision tools to approximate
20
long term effects of different soil and crop management practices. The CENTURY
ecosystem model is one of the widely used agro-ecosystem model that was
developed by Parton et al. (1987). The model simulates long term dynamic of soil
organic carbon and its different pools i.e. active pool, slow pool, passive pool and as
well as crop production in plant and soil system (Parton et al., 1988; Falloon and
Smith, 2002). The application of CENTURY carbon model is an influential tool for
imitation of long-term effects of different agricultural management practices on soil
properties and crop production under diverse ecosystems. The CENTURY carbon
model has been successfully used worldwide however there is no published literature
available on its application and performance in agro-environmental conditions of
Pakistan.
Keeping in view the above mentioned problems related to conventional
tillage system and worldwide recognition of conservation tillage through multifarious
benefits for sustainable crop production, the current investigation was planned in
dryland area of Pothwar, Pakistan to evaluate soil properties, crop production and
their long term simulation with CENTURY Carbon model under conventional and
conservation tillage systems with the following objectives.
1. To compare conventional and conservation tillage practices for their effects on
soil physical and biochemical properties.
2. To assess effect of conservation tillage on soil nutrient concentrations against
conventional tillage practices under fallow-wheat system.
3. To evaluate conservation tillage system against conventional practices for wheat
yield and economic benefit.
21
4. To validate CENTURY agro ecosystem model for long term simulation of
different soil management practices under agro-climatic conditions of Pothwar.
Hypothesis:
1. Conservation tillage system improves soil quality by increasing soil organic
carbon contents.
2. Conservation tillage system provides sufficient crop yield and economic
benefits to the farmers of dry land areas.
3. CENTURY carbon model successfully simulates long-term soil properties
and crop yield in agro-ecological condition of dryland Pothwar, Pakistan.
22
Chapter 2
REVIEW OF LITERATURE
Tillage is the most basic physical operation in world agriculture systems and
is very important for crop production. During in last decay the soil cultivation with
intensive moldboard plough remain popular in farmers communities especially its
function to moisture conservation, weed control and loosen the soil to provide better
condition for seed germination and plant growth. Injudicious and indiscriminate use
of intensive tillage not only increase the input cost of farmers but also degrade the
quality of soil and create threatened to climate change. Therefore researcher and
scientific community compelled to rethink alternative systems which improve the
soil health, environment friendly provide sufficient yield and economically feasible.
The available scientific research on tillage and crop residues management carried out
in different dryland areas are comprehensively reviewed and described below.
2.1 EFFECT ON SOIL CHEMICAL PROPERTIES
Soil organic carbon (SOC) plays an important role for sustainable crop
production (Lal, 2004). World soils can serve as big source or important reservoir of
global carbon depending on land use and management (Lal, 2005). Thus SOC have
gained considerable attention because of its great potential for sequestration of
atmospheric carbon (Baker et al., 2007). Soil structural stability protect losses of
SOC from its degradation by soil organisms (Tisdall and Oades, 1982; Beare et al.,
1994) which is evident from carbon dioxide emission observed during disturbance of
soil aggregates (Beare et al., 1994). These aggregates come out by combination of
9
23
soil particles of different sizes through organic and inorganic materials and their
stability can be used as an indicator of soil structure (Bronick and Lal, 2005;
Amezketa, 1999). Numerous researchers such as Ghuman and Sur (2001) and Shukla
et al. (2003) have observed that increased organic matter content with minimum
disturbance under conservation tillage systems increased soil aggregate stability in
the long run.
The SOC and structural stability are tremendously responsive to soil and crop
management (Blanco and Lal, 2004). Intensive tillage is cause of decline in SOC and
serious agricultural and environmental drawbacks with harmful effects on soil
fertility and productivity (Ashagrie et al., 2007); decline soil profile water contents
also enhance release of greenhouse gases (Resck et al., 2008; Lal, 2006). On the
other hand conservation tillage, which is characterized by minimum disturbance of
soil and leaving 30% crop residues at sowing time on soil surface (CTIC, 2005) have
shown great potential to increase SOC and soil quality improvement (Govaerts et
al., 2009). Crop residue also increases soil organic carbon that improves soil
aggregation (Madari et al., 2005) soil water availability (Unger, 1994; Drury et al.,
1999) number of biopores (Francis and Knight, 1993). A greater adoption of
conservation tillage could help to reduce the high risk of land degradation by wind
and water erosion in semiarid regions (Garcia-Ruiz, 2010; Lopez et al., 2001). The
short-term impact of different crop management practices on soil organic carbon
(SOC) are complex and depend on soil conditions like soil texture, structure and
related properties , climatic condition of the area , cropping system and management
of crop residues (Paustian et al., 1997; Al-Kaisi et al., 2005; Munoz et al., 2007).
24
The world carbon soil pool is composed of 60% organic and 40 % inorganic
materials. The inorganic material consist of mineral like gypsum and dolomite while
organic material composed of decomposed living material (Wood et al., 2000). Soil
organic material decomposition can be categorized into three important pools i.e.
active, slow and passive pool. The active pool is composed of microorganism and
their decomposition take few months, slow pool is composed of partially
decomposed organic material which takes few years for their decomposition and
passive pool is the most stable pool which takes longer period for their
decomposition. This stable portion is important and comprised of essential nutrient
required for plant growth (FAO, 2015). Soil organic matter contain approximately
58% carbon and 42% other vital nutrient (Berg and Laskowski, 2006).
Lal (2009) reported that use of intensive tillage resulted loss of 90 Gt of
carbon from soil during last century. Much of this carbon was lost by increasing soil
disturbance. The soil organic carbon losses through intensive agriculture
management practices have a threat to both climate change and food security. For
climate change by emission of CO2 and other gases while for food security by
declining soil fertility and breaking soil aggregate and decreasing soil water holding
capacity. The losses of soil organic carbon increase when the disruption of carbon
pools occurs by soil cultivation or other intensive crop production systems (Lal,
2007). The carbon input in agriculture system is already low because of low retention
of crop biomass due to crop harvesting then other natural systems. FAO (2015)
reported that sustainable crop production require to enhance soil organic carbon input
by retention of crop residues, applying organic amendments like composites and
25
farmyard manure and reduce its output by minimum disturbance and no-tillage. The
potential positive aspect of these material required long period for their adoption.
(Lal, 2004b) reported that regular use of these material upto 50 years will restore soil
organic carbon level upto historic level.
Researcher reported increase of soil organic carbon under conservation tillage
systems than conventional tillage. Causarano et al. (2008) studied in different row
cropping systems that soil organic carbon was 28 Mg C ha-1 under conservation
tillage systems and 22.2 Mg ha-1 under conventional. Similarly Motta et al. (2007)
after six years study reported that 3.3 Mg C ha -1 carbon increased under conservation
tillage systems than conventional systems. Puget et al. (2005) in Ohio, reported that
total organic carbon under corn residues with no-till was 12% and under plough till
was 8%.
Murillo et al. (1998) compared short term effect of conventional and
conservation tillage and reported that after 2 years surface soil organic carbon
increased 1.1% under conservation tillage and after 4 years 1.34% while in
conventional tillage systems 0.84% - 0.89% respectively two and four years. They
also reported that widespread adaptation of conservation tillage can improve soil
quality by increasing soil organic carbon contents in rainfed areas.
Vagen et al. (2005) concluded that retention of crop residues and reduction of
tillage operation under fallow wheat systems improved accumulation of carbon from
0.1 to 5.3 Mg ha-1 year -1. They also reported that retention of crop residues and other
26
organic amendment under conservation tillage system in cropland increase
accumulation of C up to 0.37 Mg ha-1 year -1. Balota et al. (2004) reported that long
term experimental results showed that retention of crop residues and no-till enhanced
total organic carbon by 54% and soil microbial biomass carbon 83% as compared to
conventional tillage at 0-50 cm depth. Soon and Arshad (2005) also reported that soil
MBC and total organic carbon was 7-36% higher under no-till (NT) than
conventional tillage (CT) but there was decreasing trend observed with repeated
tillage operation. Heenan et al. (2004) result showed that retained of crop stubbles in
combination with no-till increased 3.8 Mg ha-1
Soil organic carbon at surface while
continuous ploughing with residues burning decline SOC up to 8.2 Mg ha-1
.
Fando and Pardo (2009) investigated the effect of four different tillage
systems like no-tillage (NT), chisel plow (CP), conventional intensive tillage (CT)
and sub-soiling with a parabola (ZT) on soil chemical properties in a semi arid
environments. After five years research they conclude that no-tillage and zone tillage
systems were enhanced soil organic carbon and improved fertility of the soil also
reduced surface soil pH.
Shah et al. (2010) in uplands of Khyber Pakhtunkhwa for three years and
found that NT improved 16% SOC, 10.44% MBC and 16.87% MBN over the CT
tillage. They also reported higher SOC and TN with residue return than residue
removal and intensified cropping than fallow based cropping. Among crops legume-
cereal rotation promoted SOC than cereal-cereal rotation.
27
Nizami et al. (1995) and Nizami and Saleem (1997) studied to evaluate the
effect of crusting on crops. In first study, four soil series were investigated. Then six
soil series (including these four) namely Gulian (SiCL), Khaur (SiCL), Missa (SiL),
Pir Sabak (SiL), Balkassar (SL) and Khair (SL) were selected for the second study.
The soil treatments were: Fertilizer without hoeing (A), farmyard manure with no
hoeing (B), fertilizer + grass mulching without hoeing (C) and fertilizer with hoeing
(D). The applied nutrient status of all the treatments was kept uniform. Soil crust
intensity decreased from 6.3 to 1.5 kg cm-2 as the texture changed from SiCL to SL,
while increased with an increase in silt and clay contents and was inversely
proportional to organic matter and soil water contents. With an increase in soil crust
intensity, the plant population decreased. It was concluded that soil structure and
aggregate stability can be improved by using organic manures.
Wang et al. (2008) conducted a 16 year field experiment to evaluate the effect
of no-tillage with retention of crop residues and convention tillage with residues
removal on soil bio-chemical properties. No-tillage with retention of crop residues
increased total soil organic carbon, total nitrogen, available phosphorus and soil
microbial biomass carbon and nitrogen in upper 0-10 cm depth and increased winter
wheat yield. They suggested that no-tillage with retention of crop residues can
improve soil chemical properties, microbial biomass activity and also increased crop
yield in the rain fed dry land farming areas.
Melero et al. (2011) reported the effect of conventional tillage (CT) through
intensive moldboard plowing and reduced tillage (RT) in the form of chiseling on
28
soil properties in a dryland alkaline soil. The samples were taken upto 0-25 cm depth
from three different intervals and three different timing, after ploughing, sowing and
harvesting. The result was compared with no-tillage. Soil organic fraction found
adequate under chiseling plough and indicated changes in soil properties.
Mouldboard ploughing showed destructive effect on soil organic carbon fraction
which degrades other properties of soil.
Enfors et al. (2011) evaluated the effect of conservation tillage on yield and
soil properties in dryland farming system of Sub Saharan Africa. In three year studies
they concluded that yield was increased due to change in soil chemical,
microbiological properties however there was no change in the physical properties.
The water availability in the root zone also improved under conservation tillage
system.
Sparrow et al. (2006) evaluated long term effect of different tillage practices
with residues retained and removed. Tillage practices were no-till (NT); disk once in
spring (DO), disked twice (DT) once in spring and other in fall. After long term
study they reported that bulk density and organic matter content level increased when
residues were added. The soil microbial biomass carbon and weed population was
high under no-tillage system. Grain yield increased under disk once in spring (DO)
while there was no significantly difference in no-till and disk twice (DT). They
concluded that reduced tillage improves soil properties and yield but long term no-till
causes serious problem of weed and organic matter in the surface layer.
29
Machraoui et al. (2010) conducted an experiment to compare conservation
and conventional tillage under four crops (durum-wheat, barley, pea and oats) in
Mediterranean semi-arid conditions on soil properties and crop yield on two different
locations. After 4 years they found that the contents of some parameters of soil and
crop were greater under no-tillage than conventional tillage at 0–20 cm depth layers
but not statistically significant. They concluded that improvement of agronomic
parameters under no-till depends on type of crop and location. They suggested that
under short term study no clear benefits of no-till were found.
2.2 EFFECT ON SOIL PHYSICAL ENVIRONMENT
Land is most important fundamental physical natural gift in human mankind
but their indiscriminate use by human beings for ever increasing demands have
deteriorated its quality for life supporting systems in real sense. Research during
green revolution was conducted in comparison of conventional cultivator systems
with intensive deep moldboard for increasing higher profile moisture conservation;
reduce bulk density to provide physically better condition for plant germination and
growth. The soil cultivation with intensive moldboard plough remain popular in
farmers communities especially its effect to loose soil, enhance rain water
infiltration, moisture conservation, and weed control. Injudicious and indiscriminate
use of intensive tillage not only increase the input cost of farmers but also degrade
the quality of soil and create threat to climate change. Therefore researcher and
scientific community compelled to provide alternative systems which improve the
soil health, supply sufficient yield and economically be feasible.
30
Soil water conservation in soil profile is the major challenge (Campbell and
Akhter, 1990) due to higher evaporation than precipitation. Soil surface crusting are
other serious problems in these areas with alkaline pH and accumulation of excessive
salts (Rafiq, 1990). Commonly a hardpan is observed beneath the soil surface due to
intensive tillage and continuous plowing at same depth, which restricts the
movement of soil water and plant nutrients uptake in the deeper profile layers. The
plow-pan also decreases water infiltration and thus encourages runoff losses (Razzaq
et al., 1989).
There are numerous benefits of conservation tillage for improvement of soil
physical properties. The conservation tillage also makes the soil stable against the
deterioration by water and wind erosion (Madari et al., 2005; Chan et al., 2002)
improves soil water infiltration, decreases soil surface loss through surface cover and
improves soil water and nutrient conservation (Franzluebbers, 2002a). In
conservation tillage systems additions of crop residues play a vital role (Loveland
and Webb, 2003) The crop residues on the soil surface protect the soil from the
impact of rain drop and slow down the intensity of runoff by acting as surface barrier
(Franzluebbers, 2002b; Zhao et al., 2007) therefore increasing intake of water into
soil profile and increased in situ moisture conservation (Shaver et al., 2002),
increases and retains organic carbon in soil (Franzluebbers, 2002; Zibilske et al.,
2002), which interfere with soil physical properties (Dexter, 2004).
Blanco-Canqui and Lal (2007) evaluated soil bulk density under zero tillage
with three different levels of wheat straw i.e. 0, 8 and 16 Mg-1 yr-1 up to 10 repeated
31
years on Ohio at silty loam soil. They reported that retention of crop residues had a
greater impact on soil bulk density in the surface layer but the difference in sub
surface layer was not significant. The bulk density was gradually decreased with
retention of crop residues and their 58% low value observed under 16 Mg-1 yr-1 and
19% under 8 Mg-1 yr-1 then without retention of crop residues. The impact of crop
residues on soil bulk density was decreased with increasing depth. Their finding are
also related to (Lal, 2000) who reported that application of rice straw up to 16 Mg
ha-1 yr-1 decreased soil bulk density from 1.20-0.98 Mg ha-1 in the upper surface
layer on a sandy loam soil. Contrasting results in the literature have been reported
about bulk density under conservation tillage systems. Dao (1996) reported that
there was no significant difference in bulk densities of conservation and conventional
tillage systems while (Ball-Coelho et al., 1998; Schonning & Rasmussen, 2000)
found that bulk density was high in starting years of conservation tillage but
decreased gradually with time.
Chisel plow is a subsoil cultivation technique that cuts soil deeper with fewer
disturbances of soil aggregates than conventional tillage. Chisel plow breaks the sub-
surface compacted layer increase water infiltration rate upto lower depth, enhance
deep rokot growth development that help uptake of nutrient and water in deep layer
which improves crop production and increase grain yield (Birkas et al., 2004; Abu-
Hamdeh, 2003; Pagliai et al., 2004; Pikul and Aase, 2003; Salih et al., 1998; Xu and
Mermoud, 2003). Mwendera and Mohamed Saleem, (1997) reported that compacted
sub-surface layer created by continuous tillage operation to the same depth.
32
Shafiq et al. (1987) compared chisel plow and zero tillage with tine
cultivator. They found that chisel plow before the onset of monsoon had the highest
soil moisture content and least bulk density while ZT had the lowest moisture and
highest bulk density. Anwar-ul-Hassan (2000) after a comprehensive review about
arid and semi-arid areas of Pakistan reported that surface soil crusting is a serious
problem over 2.3 mha of dryland areas of Pakistan (Rafiq, 1990) due to low organic
matter, high silt content and sodicity. He suggested that adoption of different
management practices such as application of surface mulches and increasing organic
matter contents would help to overcome the problem.
Ijaz et al. (2007) conducted experiment using different tillage practices with
and without application of straw mulch. The MT showed significantly low fallow
efficiency and water content at wheat sowing in the two year study than conventional
practices (15-23%). However the mulch 4 Mg ha -1 and no-mulch plots did not show
significant differences for soil moisture storage. They suggested that additional
investigation is needed to explore the authentic rate of wheat straw mulch retention
and different method of residue managing to hold up rapid decomposition under
tremendous high temperature during summer season.
Shafiq et al. (1994) contrasted direct drilling with two farmer conventional
practiced i.e. conventional cultivator, Moldboard. Who found that soil moisture
content measured in June, August and December were similar under conventional
and no-till treatments. However the infiltration rates measured in the same months
were significantly higher under no-till. They also explained the reason that surface
33
vegetation encouraged the breakdown of soil crusting which ultimately reduced the
surface runoff and increased vertical flow of water in soil profile.
Nizami et al. (1989) compared three tillage practices i.e. moldboard plow,
chisel plow and tine cultivator in different soil series. They reported that influence of
different tillage practices was site specific. Chisel plow conserved more moisture in
Missa and Balkassar soils while MB plow in Guliana. Chiseling was efficient in
moisture conservation where a pan existed in profile or the soil texture was coarse.
Martınez et al. (2008) assessed a field research to see the effect of
conventional tillage and no-tillage practices on soil physical properties, wheat root
growth and yield. They found that soil aggregates stability were higher under NT at
the top 5 cm however, macro-pores and soil water infiltration was higher under
conventional tillage. Hussain et al. (2013) compared different tillage practices at the
time of wheat sowing and reported that there was no difference in soil moisture
content at different stages during wheat crop.
In conservation tillage systems retention of crop residues play crucial role, it
reduce runoff ( 1.2 to 2.2 %) and increase infiltration rate than ploughed soil (8.3 to
21.5 %) at 1 and 15% slope respectively (Rockwood and Lal, 1974). Ehlers (1979)
was also conducted experiment on silty soils at Germany to compared different
tillage systems; He reported that no-tillage improved soil structure due to increasing
concentrations of organic carbon in the soil surface. Even though total porosity was
increased by tillage, the macro pores connecting the soil surface to the subsoil were
34
enhanced and improved infiltration. Retention of crop residues also increased water
infiltration (Lang and Mallett, 1984). There was lower infiltration rate observed
under zero tillage (ZT) while ploughing with disc plough improved soil water
infiltration (Subbulakshmi, 2007).
Ling et al. (2011) after a review of conservation tillage in China concluded
that conservation tillage promotes soil and water conservation by reducing
evaporation losses, increasing moisture storage and organic matter content, slowing
down the impact of rain drop, reducing water and wind erosion, depressing weed
population and improving soil structure. They also reported that conservation tillage
improves crop production by providing better nutrient cycling and efficient use of
profile water. Furthermore, it has been found to be economically better due to
reduced input costs of fuel, labor, fertilizer and unnecessary plowing. Although it
interferes with all the environment of soil however its effects are site specific and
depend on the soil and climate of the area.
2.3 CROP PRODUCTION AND ECONOMICS
With increasing population and decreasing land owners the rainfed lands have
great potential for contributing to national food security to meet the food and fiber
demand of resource poor masses of country. Crop yield can vary from year to year
and are influenced by different factors including soil type, climate and management
practices. Mohammad et al. (2006) conducted a study for comparison of farmer’s
conventional tillage and no-tillage both with residue retention and removal on wheat
and oat crops. They reported that there was no statistically appreciable difference
35
observed in crop yields and related attributes in tilled and no-till plots. Further more
in the uplands of Pothwar Plateau Ijaz et al. (2007) conducted a two year experiment
in which the main treatments were moldboard plow, sub-soiler and conventional
cultivator with addition and removal of straw mulch. The treatments were applied at
the start of fallow period and wheat crop was sown during winter. They reported that
the minimum tillage and moldboard plow gave averagely 30% higher grain yields of
wheat than tine cultivator during both the experimental years. Grain yield was 33%
higher in mulch than no mulch. Khan et al. (2011) in Khyber Pakhtunkhwa at rainfed
conditions of Lukimarwet conducted an experiment in which zero, reduced,
conventional and maximum tillage with different doses of fertilizer N were applied at
the time of wheat sowing. The one season study indicated that germination count,
grain per spike and 1000 grain weight were similar under all tillage treatments.
However the productive tillers and wheat yield were significantly higher with
maximum tillage. Also Khattak et al. (2005) in a sandy loam soil of rainfed area of
Khyber Pakhtunkhwa compared the effects of no-tillage, chisel plow, moldboard
plow, cultivator and disk harrow on chickpea yields. They reported that maximum
chickpea yield was obtained under chisel plow that was 19% higher than the NT that
was attributed to better weed control. A long term field study (2004-09) carried out
by Mohammad et al. (2012) in the upland of Khyber Pakhtunkhwa and the
treatments were consisted in three cropping rotations: 1. fallow-wheat 2. Summer
legume-wheat 3. Summer cereal-wheat also two tillage system: 1. tillage 2. No
tillage. Crop residues retained and removed was also carried out in all management
practices. They reported that wheat straw and grain yield was equal under tilled and
no till treatments in all five years. However every year, retention of crop residues
36
was significantly improved wheat straw and grain yield. Retention of crop residues
with no-tillage resulted in 520 kg/ha higher wheat grain yield than without residues
treatment. The results of the long term study showed that no-tillage with retention of
crop residues and legume based crop rotation treatments were beneficial under the
rainfed conditions. Shafiq et al. (1987) conducted an experiment under the
environmental condition of Pothwar to assess the effect of zero tillage, cultivator and
chisel plow on the yield of wheat crop. They reported that yield was higher under
chisel plow than other treatments.
Khan et al. (2011) compared the effect of cultivator with moldboard on
mungbean yield under the rainfed conditions of Dera Ismail Khan, Khyber
Pakhtunkhwa. After two year study they concluded that yield was higher under tine
cultivator than moldboard plow. Also Razzaq et al. (2002) in a three year study at
farmer’s fields of Islamabad evaluated the effect of moldboard plow, direct drilling
and tine cultivator. They reported that yield was higher with moldboard than direct
drilling and tine cultivator. Moreover Mohammad et al. (2010) found the effect of
no-tillage and conventional tillage with and without residue on mungbean (Vigna
radiata) yield under the rainfed conditions of Khyber Pakhtunkhwa. There was
higher mungbean yield (1224 kg ha-1) obtained under no-tillage with addition of crop
residues. Also Arif et al. (2006) contrasted three tillage treatments i.e. no-tillage,
reduced tillage and chisel plow in a rainfed valley of Peshawar, Khyber
Pakhtunkhwa. They concluded that the fodder maize yield was significantly higher
under reduced tillage. However in case of groundnut yield has been found to be
better with moldboard plow than chisel plow under rainfed condition of Chakwal,
37
Pothwar (Akhtar et al., 2005). Also Ijaz et al. (2010) were carried out three year field
experiments at three different locations (Fateh Jang, Chakwal and Rawalpindi). The
experimental treatments were arranged in split–plot design as follows: Moldboard
plow, minimum tillage and conventional cultivator in main plots; fallowed by
legume crop and mulch of wheat straw were used in sub plots. Wheat crop was
planted in all the subplots during winter season. The wheat crop biomass and grain
yields were statistically equal under all the applied treatments. The average yields
were (7.37, 6.19 and 4.27 Mg ha-1 for wheat biomass and 3.06, 3.56 and 1.6 Mg ha–
1 for wheat grain yield at all sites respectively under moldboard plough, minimum
tillage and conventional cultivator. Also Ali et al. (2013) conducted field study
during 2005 through 2007 at two locations (Rawalpindi and Fatehjang) in Pothwar,
Pakistan to compare minimum tillage with conventional tillage practices for yield
performance of mungbean (Vigna radiata). The treatments including minimum
tillage (MT), conventional cultivator (CC) and moldboard plow (MP) were laid out
in a randomized complete block design. The biomass and grain yields were generally
equal under all the tillage treatments. The average values were 3.10, 3.19, 3.64 Mg
ha-1 for biomass and 0.59, 0.58, 0.60 Mg ha-1 for grain yield under MT, CC and MP
respectively.
Matocha et al. (1997) concluded that method of primary tillage usually has
little or no effect on final grain yields except in droughty seasons when yield
reductions were associated with deep primary tillage with either moldboard or chisel
plows. A minimum tillage system developed for Southern Texas produced 110% of
38
the conventional tillage system corn yields in seasons with sub-average precipitation
and 101% with above average precipitation.
There was contradictory reported observed under different tillage systems,
some researcher reported no differences in cereal crop production between different
tillage systems (Schillinger, 2001; Unger, 1994) other researchers observed better
crop yield under no-tillage (Lawrence et al., 1994; Bonfil et al., 1999). There were
no clear differences observed in crop yield among different tillage systems (Moret et
al., 2001). The finding of Anschütz et al. (2003) suggests that conservation tillage
systems perform best as an alternative to conventional tillage for fallow management
in semiarid dryland cereal production areas in central Aragon.
Li et al. (2007) conducted long term experiment during (1994-2006) at loess
plateau of China and reported that mean yield of conservation tillage was 19% higher
than traditional tillage practices. They also reported that yield was 8% low at the start
of experiment under conservation tillage system but with passage of time the yield
was improved under conservation tillage and after six years it reached upto
significant level. They say that conservation tillage performed better during drier
season when there was low rainfall.
Zhang et al. (2009) also studied that tillage operation had minute effect on
increasing crop yield in previous 2-3 years but yield was significantly improved with
increasing time. They say that average wheat yield during (1999-2009) was 3.5% and
maize yield was 1.4% higher under conservation tillage then conventional practices.
39
They declared that yield was 6.2% improved under conservation tillage in last six
years but in previous years the yield was same under conservation and conventional
tillage systems.
Hemat et al. (2006) evaluated a short term experiment during 3 years. Their
treatments were moldboard plough, chisel plough, minimum tillage and no-till with
stubble and crop residues. They reported that average three years grain yield was 1.4
Mg ha-1 under no-till with crop residues, 1.3 Mg ha-1 for chisel plough and 1 Mg ha-1
for conventional moldboard systems. The crop yield was significantly (25-40%)
improved under conservation systems then conventional tillage. They also reported
that conservation tillage practices performed better during dry season where the
precipitation was low. The trend was also remained same for crop biomass that no-
till and chisel plough with residues performed better than conventional moldboard.
Increasing costs of inputs such as fuel, fertilizer and seed have rendered the
dryland farming a profitless business for small landholders. Therefore lowering the
input cost of dryland agriculture is need of the time. Arif et al. (2007) compared
economics of no-till, tine cultivator and chisel plow. They reported that the no-till
with efficiency coefficient of 1:4 was found to be economically more feasible for
resource less farmers although gross margins and gross income was higher with tine
cultivator. Also Ahmed et al. (2007) evaluated bed planting, zero tillage and
conventional tillage in rainfed area of Islamabad and reported that zero tillage gave
maximum net income by decreasing input cost. In Pakistan and India at rice-wheat
system Hobbs and Gupta (2004) reported that zero tillage reduces the cost of
40
production up to $ 60 mostly due to decreasing fuel cost by 60-80 L per hectare and
labor cost.
Worldover, conservation tillage is practiced on about 125 million hector
(Derpsch and Friedrich 2010) out of which 96% lies in Americas, Canada and
Australia. In contrast Asia covers only 2.2% which indicates huge lag and missed
opportunity. In Pakistan, most of the studies regarding tillage systems focused yield
improvements but information on their effects on soil quality is scarce (Derpsch and
Friedrich 2009).
2.4 SOIL PROPERTIES AND CROP YIELD SIMULATIONS
Land degradation through soil erosion and use of intensive conventional clean
cultivation systems are the major problem of declining crop yield and environmental
drawback. The land can be restored and crop production will be increased by
reducing extensive tillage, retention of crop residues and crop diversification (Gomez
et al., 1996). However, the benefits of these tillage systems are usually expected to
appear after their long term use. Computer based models are robust and cheap
decision tools to estimate long term effects of different soil and crop management
practices. The CENTURY ecosystem model is one of the widely used agro-
ecosystem that was developed by (Parton et al., 1987). The model simulates long
term dynamic of carbon, nitrogen, phosphorus, sulfur, water budget, leaching and
soil temperature along with crop production in plant and soil system (Parton et al.,
1988; Falloon and Smith, 2002).
41
Leite et al. (2003) simulated SOC by CENTURY model under disc plow and
no-tillage. The slow, active and passive pools of C stock and organic carbon were
simulated by CENTURY model. The simulated results were satisfactorily fitted with
measured data and showed recovery of soil C stock under no-tillage.
Fuentes et al. (2009) validated CENTURY model in Mediterranean semi arid
environment and compared three different tillage systems no-tillage (NT), reduced
tillage (RT), conventional tillage (CT) and two cropping systems barley-fallow,
continues barley effects on soil organic carbon. The comparison of calculated and
estimated values showed a significant correlation. They found that carbon level
increase in NT and RT as compared to CT.
The CENTURY carbon model (Parton et al., 1988, 1987) is one of the most
widely used worldwide and well validated soil organic matter under different
ecosystem. It has been used to estimate changes in SOC and their pool under crop
land in long-term field experiments. It simulate active pools which take few month
their decomposition, slow pool which take few month to few years their
decomposition and passive pool which take longer period for their decomposition.
CENTURY is being used increasingly in studies of SOC dynamics (Skjemstad et al.,
2004: Falloon and Smith, 2002).
Kelly et al. (1997) used CENTURY carbon model for simulations of long-
term data sets. They reported that model effectively simulates soil organic carbon
under different agro- climatic condition. Soil organic carbon simulations were also
42
found to be the most successful in forest, grass and crop systems. Though, the
CENTURY carbon model was failed to confine acute values of yield however annual
averages were quite comparable between observations and simulations, leading to
reasonable estimates of soil organic carbon. The model effectively simulates SOC
changes across different type of land uses and climatic condition. They propose that
CENTURY model is a use full tool for predicting future scenario and land
management strategies.
Tittonell et al. (2006) validated the CENTURY carbon model and reported
next 50 years scenario that SOM is the indicator for soil quality and their increase
and decrease depends upon agriculture management practices. Future simulation
demonstrates variation of SOM and model will help as decision tool for future
strategies.
Parton et al. (2004) reported that CENTURY carbon was used to estimate
carbon dynamic during 18th – 21st century under changing climate and improved
management practices. Their results demonstrate that before 20th century there was
0.477 G tons carbon was lost. They also reported that in future retention of crop
residues, crop rotation and minimum disturbance will restore 0.116 G tons carbon
upto the end of this century.
Sobocka et al. (2007) predict information (2005-2090) regarding different
soil organic carbon pool under different crop management practices. The reported
that simulated trend indicate that carbon in active and slow pool will not significantly
43
decrease but carbon in passive pool will drastically decline under the scenario of
climate change but this change was not observed under total soil organic carbon.
Chong-sheng et al. (2008) studied the long-term SOC evolution in Chinese
Mollisol farm land, the results provided an optimal way for maintaining SOC in
Chinese Mollisol farm Land. To increase, as much as possible within agro-
ecosystem, soil organic matter returns such as crop stubble, crop litter, crop straw or
stalk, and manure, besides applying chemical nitrogen and phosphorous, which
increased system productivity and maintained SOC content as well.
The available literature studied regarding conservation tillage and
conventional tillage for their effect on soil properties and crop production indicate
that
1) Most of the research work in dryland areas of Pakistan is short term.
2) The majority of the research work was focused on crop yield but little
information is available regarding soil organic carbon fractions.
3) There is no literature available regarding long term simulation of soil
properties and crop yield through computer base model under
conservation tillage in dryland areas of Pakistan.
44
Chapter 3
MATERIAL AND METHODS
3.1 SITE DESCRIPTION
Conservation tillage experiment was initiated in 2012 on a sandy clay loam
soil of Kahuta soil series belonging to Udic Haplustalfs at PMAS-Arid Agriculture
University Research Farm Chakwal Road (latitude 33°36’0”N, longitude 73°02’0”E)
in semi-arid dryland Pothwar, northern Punjab, Pakistan. The soil consists of 560 g
kg-1 sand, 190 g kg-1 silt and 250 g kg-1 clay, pH 7.85 and SOC 5.2 g kg-1 (Table 1).
The climate of the experimental site was semi-arid, very hot in summer and cold in
winter with 70% of the rain received during monsoon in the form of heavy showers
(Figure 1). The farmers of this area conventionally use intensive moldboard plow at
the onset of monsoon, followed by 8-10 ploughings with tine cultivator in fallow-
wheat systems for weed control, moisture conservation and seed bed preparation.
3.2 TREATMENTS DETAIL
Two years experiment was carried out from 2012-13 to 2013-14 under
fallow-wheat cropping system. The experiment was conducted under split plot design
and each treatment replicated four times. The total experimental area was 100 m × 60
m (6000 m2) which was divided into sixteen main plots of 27 m × 11 m (297m2) and
each main plot was divided into equal halves as sub plots.
The main plot were tillage treatment, conventional tillage (CT), minimum
tillage (MT), reduced tillage (RT) and zero tillage (ZT), sub plot-treatments in each
31
45
tillage had residues retained (R+) or residues removed (R-). One year earlier than
installation of treatments, the field was left without tillage and crop to offset the
residual effects of previous tillage practices.
In CT plots, the soil was ploughed with moldboard plow at the start of
monsoon followed by 8-10 time shallow cultivation with tine cultivator applied after
each major rainfall for weed control and moisture conservation. Wheat sowing in
these plots was done with seed-cum-fertilizer drill. In MT, the field was also
ploughed with intensive moldboard on the onset of monsoon and four time
cultivation with tine cultivator, while sowing was done with conventional seed-cum-
fertilizer drill. In RT, one time chisel plough was applied at the start of monsoon and
then during fallow period weeds were controlled with roundup herbicide (Glyphosate
@ 1 L acre-1) and wheat was sown through direct drilling with zero tillage drill. In
ZT, field remained undisturbed for entire fallow period and weeds were controlled
with roundup herbicide when needed. Winter wheat was directly sown with zero
tillage drill. In sub-plot treatments +R involved harvest just spikes from the previous
crop and retention of all the stubbles in field. In case of -R the crop was harvested
with reaper and there was no crop residues left in field except stubbles. The
recommended doses of fertilizer NPK i.e. 100-60-30 in the form of urea, diamonium
phosphate (DAP) and sulfate of potash (SOP) were used. Wheat was planted at seed
rate of 100 kg ha-1.
3.3 SOIL SAMPLING
Soil samples were collected from each replicated plot. Samples were taken
46
through different tools for different purposes. Samples for texture, soil pH, electrical
conductivity, Total Organic Carbon (TOC), Microbial Biomass Carbon (MBC),
Particulate Organic Carbon (POC), Mineral Associated Organic Carbon (MAOC),
total N, available P and extractable K samples were taken through soil auger. For
water content up to 90 cm depth in soil, tube sampler was used, for bulk density and
aggregate stability, samples was taken through core sampler. After collection and
preparation of soil samples following analyses were carried out.
3.4 CHEMICAL ANALYSES
3.4.1 Total Organic Carbon
One gram of dry soil sample was taken in to a 500 ml conical flask. Ten
drops of 1 N potassium dichromate along with 20 ml concentration H2SO4 was
added. The suspension was mixed and allowed to stand for 30 min. After cooling 200
ml DI water was added and 10 ml of orthophosphoric acid was added and allowed to
cool. Then 10-15 drops of diphenylamine was added as indicator and the flask was
placed on magnetic stirrer. After stirring 0.5 M ferrous ammonium sulfate was
added so that colour changed from blue to green (Walkley, 1947). Total organic
carbon was calculated by formula:
Total organic carbon (%) = 1.334 × oxidizable organic carbon
(Vb-Vs) × 0.3 × M)
Oxidizable organic carbon (%) = ---------------------
Wt of oven dry soil
M = 10/Vb
Where
47
Vb = Volume of ferrous ammonium sulphate to titrate the blank
Vs = Volume of ferrous ammonium sulphate to titrate the sample
M = Molarity of ferrous ammonium sulphate
The calculated oxidizable organic carbon was multiplied by 100 and also
converted in to g kg-1 and for higher values in to Mg ha-1.
3.4.2 Microbial Biomass Carbon
Microbial biomass carbon was measured through fumigation extract method.
Ten gram fresh soil sample was taken in 50 ml beaker and other 10 g into 125 ml
water–tight bottle. Then 30 ml alcohol free chloroform was taken in another 50 ml
beaker and placed in desiccator for fumigation at 25 °C for 24 h. After fumigation
the sample was extracted with 50 ml 0.5 M K2SO4 and shaken upto 30 min and
filtered. Another 10 g soil was extracted similarly but without fumigation. Then 4 ml
of sample extract was transferred to a digestion tube and 1 ml of 0.0667 M potassium
dichromate was added. Slowly 5 ml concentration H2SO4 was added and heat at 150
°C for 30 min. The contents were transferred into 100 ml conical flask and supplied
3-4 drop of indicator O-phenanthroline monohydrate. Then titration was done with
ferrous ammonium sulphate solution (Anderson and Ingram, 1993).
3.4.3 Particulate Organic Carbon
Twenty five gram of soil sample was transferred into a 500 ml flask and
added 200ml sodium hexametaphosphate solution, placed on mechanical shaker for
30 minutes. Soil suspension was then washed through a 53 micro meter sieve and the
48
coarse fraction was separated. The soil samples above the 53μm sieve were
considered particulate soil organic carbon and were oven dried at 45 oC and was
anlysed for carbon (Cambardella and Elliott, 1992).
3.4.4 Mineral Associated Organic Carbon
Ten gram of soil sample was transferred into beaker and added 30 ml sodium
hexameta phosphate solution, placed on mechanical shaker for 30 minutes. Soil
suspension was then washed through a 53 micro meter sieve and the coarse fraction
was separated, and was oven dried at 45 oC and was analyzed for carbon
(Cambardella and Elliott, 1992).
3.5 SOIL FERTILITY EVALUATION
For nitrate-N 0.2 g soil sample was digested at 360 °C with 4.4 ml mixture of
selenium powder, lithium sulphate and hydrogen per oxide. The sample was allowed
to cool and volume was made up to 100 ml. After the settlements of the clear
solution, absorbance was measured by spectrophotometer at 665 nm (Anderson and
Ingram, 1993).
For soil phosphorus, five gram of soil sample was taken in a 250 ml
Erlenmeyer flask and 100 ml 0.5 M sodium bicarbonate solution was added. The
solution was filtered and 10 ml of clear filtrate was taken through pipette into 50 ml
volumetric flask. One ml of 5 N H2SO4 and also 8 ml of ascorbic acid were added.
Then volume up to 50 ml was made. Potassium dihydrogen phosphate (2.5 g) was
dried in oven. After cooling, 2.197 g was dissolved in distilled water by bringing to 1
49
L, this solution contained 500 ppm P. For preparing series of standard solutions, the
dilution of stock solution was done through adding its 50 ml into 250 ml flask and
bringing to volume, this solution contained 100 ppm P. After dilution series of
standards 1, 2, 3, 4, 5 ppm was prepared through dilution of 5, 10, 15, 20 and 25 ml
diluted stock solution to 50 ml flask. The reading of the standards and samples was
recorded by spectrophotometer at 880 -720 nm (Kuo, 1996).
For extractable potassium, five gram of air dried soil sample was taken into
50 ml centrifuge tube, then 33 ml 1N ammonium acetate solution prepared by adding
57 ml acetic acid, 800 ml DI water and 68 ml concentrated ammonium hydroxide.
After shaking extract was taken in a volumetric flask and passed through filter paper.
Then 100 ml ammonium acetate was added and concentration of K in soil extract
was determined by flame photometer (Richards, 1977).
For soil pH thirty gram of soil sample was taken in 100 ml beaker. Then 60
ml water was added and stirred with glass rod. After leaving for 1 hour pH was
measured by pH meter (Thomas, 1996).
3.6 SOIL PHYSICAL ANALYSES
For soil aggregate stability was determined by sieving 4 gram soil in wet
sieving apparatus. The soil sample was prepared by passing through 2 mm sieve and
retained in 1 mm sieve. The sample was then placed in 0.25 mm sieve and
mechanically agitated (vertical displacement) for 3 minutes. The soil aggregates
retained in the sieve was dispersed with a 1N sodium hexametaphosphate and
50
Table 1. Physico-chemical properties of experimental soil
Characteristics Value
Sand 56.0%
Silt 22.8%
Clay 21.2%
Texture Sandy clay loam
Bulk density 1.47 Mg m-3
ECe (1:1) 0.53 dS m-1
pH(1:1) 7.87
Total Organic Carbon 5.06 g kg-1
MBC 130 mg kg-1
POC 1.15 g kg-1
MOC 3.8 g kg-1
Nitrate-N 3.90 mg kg-1
Available P 3.12 mg kg-1
Extractable K 126 mg kg-1
51
relocated in the same sieve to again agitate for sand separation. The soil collected in
the can was oven-dried, weighed and aggregated stability was calculated (Yoder,
1936).
Aggregate stability (%) = (X/Y) × 100
Where
X = The amount of soil aggregates after oven drying
Y = Total weight of soil taken for aggregate analysis
Soil water contents were measured by using the formula
Wet soil – dry soil
Soil water contents = ----------------------
Dry soil
The calculated soil water contents were multiplied into 100 and also
converted into volumetric water contents by multiplying soil bulk density of the
respected depth.
Soil bulk density was measured by core sampler was pressed into soil so that
inner metal cylinder was filled uniformly. The soil was carefully removed from the
inner cylinder. After weighting sample was kept in oven at 105°C. Bulk density was
calculated by dividing weight of oven dry soil with volume of core sampler
(Campbell and Henshall, 1991).
Soil temperature was measured upto 45 cm depth by soil thermometer. Soil
52
surface covered was measured by opened the tap on the soil surface across rows and
marker points with crop residue at the soil surface were counted (Morrison et al.,
1993).
Soil texture was measured by taking forty gram of soil, treated with 30 ml
H2O2 for overnight to removing organic carbon. Sixty ml of sodium
hexametaphosphate was added, shaken and transferred into graduated cylinder to
make the volume up to 1000 ml. Density was recorded by hydrometer at specific
intervals and soil textural class was determined by textural triangle (Bouyoucos,
1927).
Infiltration rate was measured by single ring method. After removing surface
litter wet the area and ring was vertically drived in to the soil and fill up to 10 cm
water. Refill if needed and time and water level was recorded upto coming steady
state level (Berryman et al., 1974).
3.7 CROP GROWTH PARAMETERS
The crop production related parameters sample were collected by randomly
casting the square quadrate of 1 m2 at three places in each replication of the
treatments. For crop biomass plant samples were placed in oven, dry weighed was
measured and for yield grains were separated from spikes and average grain yield
was presented in Mg ha-1.
Harvest index was calculated by the formula
Harvest index (%) = (Wheat grain yield /Crop biomass) × 100
53
3.8 ECONOMIC ANALYSIS
The profitability of different tillage with and without crop residues was
determined to calculate gross margin and efficiency co-efficient. Scott (2001)
defined the gross margin as it is not equal to gross profit because it did not comprise
fixed or overhead cost such as downgrading, permanent labour cost, sum of interest.
The gross margin was calculated by subtracting variable cost from gross income. The
variable cost included tillage operation cost, weedicide, fertilizer cost, seeding cost
and harvesting cost. Gross income was calculated by total income from grain yield
and wheat straw.
The efficiency co-efficient demonstrate the profit per investment and was
calculated by dividing gross income with the total variable cost incurred for
achieving that income. The input costs and output prices used during economic
analysis were recorded during experiment (Table 2).
3.9 PARAMETRIZATION AND VALIDATION OF CENTURY MODEL
The parameterization of CENTURY model was performed by updating site
file and weather related files. The description of the experimental area was provided
to the model through site file such as latitude, longitude, sand, silt and clay
percentage, pH and bulk density etc (Table 2). The other parameters such as external
nutrient inputs, initial values of organic carbon, primary parameters of forest organic
carbon, mineral and water initials were taken as default. The previous 30 years
weather data as well as that of experimental years was collected from Agromet
Centre Chakwal that is located 40 km away from experimental site and provided to
54
Table 2. Detail of inputs and outputs under different tillage treatments used for
economic analyses
Detail of Inputs and Outputs 2012-13 2013-14
Inputs (Rs.)*
M.B Plough /hr 1200 1400
Roundup Spray /L) 1050 110
Cultivator /hr 1000 1200
Seed drill 1200 1200
Fertilizer DAP/50 kg 4500 4500
Fertilizer Urea /50 kg 2000 2000
Seed /50 kg 2500 2800
Fungicide /L 600 700
Harvest /hr 1800 2200
Threshing /hr 2100 2400
Outputs (Rs.)
Grain yield/40 kg 1200 1200
Straw yield/40 kg 320 350
* = Rs (Pakistani rupees) 1 US$ = 98 Rs
55
model in terms of monthly precipitation and minimum and maximum monthly
temperatures (Appendix 29). Input Values required for CENTURY model
parameterization provided through 12 data files. Within each file there were multiple
options in which the variables were defined for different variations of the event. For
example within CULT.100 file there are different cultivation options such as
ploughing or sweep tillage, similarly FERT.100 file is used to simulate fertilizer
according to crop requirement. These files were updated through FILE100 program.
For model validation and simulation there were six blocks of different
management events scheduled and provided to the CENTURY carbon model through
their programming pre-processor called as EVENT100. Initial four blocks were made
based on previous historical back ground of the experimental area to initiate the
model according to our environmental conditions. Fifth block was scheduled for the
experiment period and last sixth blocks were scheduled to continue the experimental
treatments for future 100 years (Table 3). In EVENT100 a grid like display allowed
the user to scheduled different management practices like cultivation, addition of
fertilizer, organic matter, sowing and harvesting time, crop type on their relevant
month and year. After scheduling, the CENTURY carbon model was run using
different sub-models for organic matter dynamics and plant production. The organic
matter sub-model divides soil organic carbon into three different pools: active, slow
and passive. The active fraction includes the soil microbes and microbial products
and turn over time of months to a few years depending on soil texture and climatic
conditions. The slow pool includes resistant plant material derived from the
structural pool and soil-stabilized microbial products derived from the active and
surface microbe pools and turnover time of 20 to 50 years.
56
Table 3. Blocks of schedule files
Blocks Years Management Repeating
sequence
1 0-1920 Grass with grazing 1
2 1921-1950 Low yielding wheat along with manures 2
3 1951-1980 Medium yielding wheat with manures and
fertilizers at minimum production level
2
4 1981 to 2010 High yielding wheat with fertilizers at 75%
production level.
2
5 2011-2015 Experiment 5
6 2016-2100 Long term simulation
57
The passive pool resistant to decomposition and includes physically and chemically
stabilized SOM and turnover time of 400 to 2000 years. After successful simulation
the outcome of model at 2013-14 during experimental years were statistically
compared to our actual calculated results. After that the simulations were run for next
coming 100 years under conservation and conventional tillage practices to estimate
the long term effects of these practices on different soil properties.
3.9 METROLOGICAL DATA
Metrological data on temperature, rain fall during experimental year (Figure
1) was collected from agro-metrological centre at Chakwal. The 30 years previous
weather data was also collected and provided to the model.
3.10 STATISTICAL ANALYSIS
The data collected for various parameters was subjected to analysis of
variance (ANOVA) under split-plot design and means was compared at 5% level of
significance by Least Significance Difference (LSD) test (Steel et al., 1997). The
correlation and regression analysis was also carried out for simulated and actual
values.
58
Figure1. Monthly rainfall and mean maximum and minimum temperatures during the experimental period
0.00
5.00
10.00
15.00
20.00
25.00
30.00
35.00
40.00
45.00
0
20
40
60
80
100
120
140
160
180
May
-12
Jun
JUL
AU
G
SE
P
OC
T
NO
V
DE
C
JAN
FE
B
MA
R
Ap
r
May
-13
Jun
JUL
AU
G
SE
P
OC
T
NO
V
DE
C
JAN
FE
B
MA
R
Ap
r
May
-14
Tem
peratu
re (
oC
)
Rain
fall
(m
m)
Rainfall (mm)
Min. Temp. (oC)
Max. Temp
59
Chapter 4
RESULTS AND DISCUSSION
4.1 SOIL ORGANIC CARBON AND ITS POOLS
4.1.1 Total Organic Carbon
The TOC was significantly affected by different tillage systems and residue
management practices during second experimental year (Figure 2b). In first year the
differences in TOC (Figure 2a) were found to be non significant though it was
numerically higher in ZT and RT with residue return than other treatments. By the
end of second year, statistically appreciable increase in TOC under ZT of 15.84 Mg
ha-1 and under RT of 14.21Mg ha-1 with residue was recorded than CT of 11.70 Mg
ha-1. It was important to note that all tillage systems showed similar TOC contents
when no residue was returned.
In semiarid areas, the greater accumulation of SOC under long term
application of conservation tillage than conventional practices has been repeatedly
reported (Alvaro-Fuentes et al., 2008; Hernanz et al., 2009; Fando and Pardo, 2011),
however build up of SOC in this short term study is encouraging. Under intensive
tillage (e.g., CT) crop residues become mixed and incorporated with the soil,
whereas under ZT and RT they are left on the soil surface. Thus, slower residue
decomposition rates under ZT and RT lead to a greater SOC accumulation in the
topsoil (Alvaro-Fuentes et al., 2008).
4.1.2 Microbial Biomass Carbon
46
60
Figure 2. Total organic carbon concentration under the tillage treatements with and
without crop residue was gradually improved with reduction of tillage and
retention of crop residue.
aa a
aa a
a
a
10
12
14
16
18
Without residue
With residue
c c
cbcbc
bc
aa
10
12
14
16
18
Conventional
tillage
Minimum
tillage
Reduced tillage Zero tillage
To
tal
org
anic
car
bo
n (
Mg
ha
-1)
(a)
(b)
2012-13
2013-14
61
The soil MBC was significantly affected by different tillage systems and crop
residue management practices (Figure 3b).The ZT gave highest amount of MBC
(0.95 Mg ha-1) followed by RT (0.81 Mg ha-1) both with retention of crop residue,
whereas CT without return of crop residues gave the lowest amount of MBC (0.28
Mg ha-1). Overall MBC contents improved with reduction in tillage in order of ZT >
RT > MT > CT and crop residue retention.
Soil microbial biomass carbon respond quickly to changes in soil
management practices (Biederbeck et al., 2005) and is proposed as more sensitive
indicator of the changes in soil quality as affected by different soil management
practices (Nannipieri et al., 2003; Filip et al., 2002). The pronounced increase in
MBC concentration under ZT and RT tillage systems could be attributed to less
physical disintegration of organic matter as well as organic matter addition as crop
residue which resulted in accumulation of active SOC pool. The MBC was
significantly correlate ( r = 0.74) with TOC (Appendix 27) as the organic matter
serves as a source of energy for soil microorganisms, its availability led to
accumulation of more microbial biomass in surface soil (Wright et al., 2005).
4.1.3 Particulate Organic Carbon
Particulate organic carbon increased gradually and at the end of 2nd
experimental year significantly higher under ZT and RT was recorded (4.54 Mg ha-1
and 4.08 Mg ha-1, respectively) when residue retained while other treatments showed
non-significant differences. The lowest amount of POC (2.61 Mg ha-1) was observed
62
Figure 3. Microbial biomass carbon concentration under the tillage treatements with
and without crop residue was gradually improved with reduction of tillage and
retention of crop residue.
a
a
a
a
a
a
a
a
0.2
0.4
0.6
0.8
1
Without residue
With residue
b
b
bc
bc
bc
bc
a
a
0.2
0.4
0.6
0.8
1
Conventional
tillage
Minimum
tillage
Reduced tillage Zero tillage
Mic
rob
ial
bio
mas
s ca
rbo
n (
Mg
ha
-1)
(a) 2012-13
(b) 2013-14
63
under conventional tillage without retention of crop residues. The two year data
showed very pronounced effect of crop residue return in ZT and RT tillage systems
on POC contents. In present study POC under ZT and RT was mainly improved
when residues were retained and significantly correlate (r = 68) with TOC (Appendix
27). According to Yoo and Wander (2008) POC increases due to roots and crop
residues left after the wheat harvest. The POC fraction in this experiment represented
9-30% of the total SOC that is in agreement with typical values of 10-30% as
reported in the literature (Wander, 2004; Alvaro-Fuentes et al., 2008; Martin-
Lammerding et al., 2011). However, despite its small proportion, it has a large effect
on structural stability and nutrient-supply ability of soils for which it is considered a
key attribute of soil quality (Haynes, 2005).
4.1.4 Mineral Associated Organic Carbon
The mineral-associated SOC in the top soil layer did not change with tillage
systems and residue management in both years (Figure 5a and b). Although values
were improved numerically with retention of crop residues and reduction of tillage
operations but the change was not sufficient to produce statistically appreciable
differences. The maximum amount of MOC (10 Mg ha-1) was observed under ZT
followed by RT with retention of crop residues. The least amount (9 Mg ha-1) was
observed under conventional tillage without retention of crop residues.
The higher proportion of carbon in MOC fractions than in labile fractions is
probably due to climatic conditions i.e. high temperature favorable to organic matter
decomposition and transformation to MOC. In our study the non- significant effect
64
Figure 4. Particulate organic carbon concentration under the tillage treatements with
and without crop residue was gradually improved with reduction of tillage and
retention of crop residue.
a aa a
a a
aa
1
2
3
4
5
Without residue
With residue
bb
bb
bb
a
a
1
2
3
4
5
Conventional
tillage
Minimum tillage Reduced tillage Zero tillage
Par
ticu
late
org
anic
car
bo
n (
Mg
ha
-1)
(a) 2012-13
(b) 2013-14
65
Figure 5. Mineral associated organic carbon concentration under the tillage
treatements with and without crop residue was gradually improved with reduction of
tillage and retention of crop residue.
aa
aaa a a a
4
6
8
10
12
Without residue
With residue
a aa
aa a
aa
4
6
8
10
12
Conventional
tillage
Minimum
tillage
Reduced tillage Zero tillage
Min
eral
Ass
oci
ated
org
anic
car
bon
(M
g h
a-1
) (a) 2012-13
(b) 2013-14
66
of tillage on MOC was probably due to short duration of study as well as physical
and chemical stability of SOM to biological decomposition. Parfitt et al. (1997)
reported that variable charge mineral and soil organic matter inter actions can
promote a great soil organic matter protection against biological decomposition.
4.2 SOIL FERTILITY STATUS
4.2.1 Soil Nitrate- Nitrogen
The soil nitrate-nitrogen was significantly enhanced by ZT and RT (Figure
6b) especially with retention of crop residues (5.52 mg kg -1 and 5.41 mg kg -1
respectively) whereas other treatments showed no significant difference. The lowest
amount of total nitrogen (3.91 mg kg -1) was observed under conventional moldboard
systems without retention of crop residues. The two years data showed that retention
of crop residues in ZT and RT plots have pronounced affect on soil total nitrogen but
all tillage systems without retention of crop residues showed similar result.
The increasing trend of total soil nitrogen with residues retention in all tillage
systems is related to the fact that the crop residues incorporated into soil, increased
organic matter contents and enhanced soil nitrogen fertility. The decomposition of
organic matter helped to increased nitrogen in soil. Crop residues play an important
role for enhancing soil organic carbon. Our results are also relevant to the findings of
Shah et al. (2003), Surekha et al. (2003) and Kumar and Goh (2002) who reported
that retention of crop residues increased total soil nitrogen than without retention of
crop residues. Peoples and Craswell (1992), Al-Kaisi and Yan (2005) also concluded
that crop residues increased soil nitrogen contents.
67
Figure 6. Nitrate-Nitrogen concentration under the tillage treatements with and
without crop residue was gradually improved with reduction of tillage and retention
of crop residue.
a a a aa aa a
1
2
3
4
5
6
Without residue
With residue
b b b bb b
aa
1
2
3
4
5
6
Conventional
tillage
Minimum tillage Reduced tillage Zero tillage
Nit
rate
Nit
rog
en (
mg
kg
-1)
(a) 2012-13
(b) 2013-14
68
4.2.2 Available Phosphorus
The available phosphorus contents also gradually increased in all tillage
systems with retention of crop residues (Figure 7b). At the end of 2nd experimental
year the values were significantly higher under ZT (4.82 mg kg -1) followed by RT
(4.40 mg kg -1) but the difference was not statistically appreciable under MT (3.89
mg kg -1) and CT (3.48 mg kg -1) tillage systems with retention of crop residues.
There was lower amount of available phosphorus under all tillage systems
without retention of crop residue. The two years data of different tillage systems also
demonstrate that retention of crop residues have obvious effect on soil available
phosphorus contents then without retention of crop residues. The reason for
increasing available phosphorus contents in soil under different tillage systems with
retention of crop residues is enhanced soil organic matter contents. It may be release
of carbonic acid during decomposition of crop residues which ultimately increased
available phosphorus contents in soil. The crop residue is also energy source of
micro organism and can help for releasing phosphorus. The result is also in line of
Gangwar et al. (2006) who reported that increasing organic matter contents enhanced
soil available phosphorus contents.
4.2.3 Extractable Potassium
The extractable soil potassium was not significantly affected by different
tillage systems with and without retention of crop residues (Figure 8a and b). Higher
numerical values were observed under MT (152.87 mg kg -1) followed by CT
(148.98 mg kg -1), RT (145.08 mg kg -1) then ZT (138.59 mg kg -1) with retention
69
Figure 7. Available phosphorus concentration under the tillage treatements with and
without crop residue was gradually improved with reduction of tillage and retention
of crop residue.
a a
aaa a
aa
1
2
3
4
5
Without residue
With residue
b bb bb
b
a
a
1
2
3
4
5
Conventional
tillage
Minimum tillage Reduced tillage Zero tillage
Av
aila
ble
ph
osp
ho
rus
(mg
kg
-1)
(a) 2012-13
(b) 2013-14
70
Figure 8. Extractable potassium concentration under the tillage treatements with and
without crop residue was not effected by different tillage systems and residues
management.
a a aa
aa a
a
0
50
100
150
200
Without residue
With residue
a
aa
a
aa
aa
0
50
100
150
200
Conventional
tillage
Minimum
tillage
Reduced tillage Zero tillage
Ex
trac
tab
le p
ota
ssiu
m (
mg
kg
-1)
(a) 2012-13
(b) 2013-14
71
of crop residues. The least extractable potassium contents were observed without
retention of crop residues and especially under ZT (123.01 mg kg -1). The two years
data of different tillage systems demonstrate that retention of crop residues with
ploughing increased extractable potassium contents in soil than zero tillage systems.
The increased extractable potassium contents with retention of crop residues have
already been reported by Gangwar et al. (2006).
4.3 SOIL PHYSICAL PROPERTIES
4.3.1 Soil Structural Stability
The two years data in Figure 9a and b showed that the highest percentage of
water stable aggregates was observed under ZT and RT with retention of crop
residues (35.7% and 33.8% respectively). The least amount of 23.12% was observed
under CT without crop residue retention.
Compared with ZT and RT, the decrease of structural stability in CT could be
attributed to two factors: i) continuous ploughing; ii) decreasing the concentrations of
binding agents. Soil structure is important for sustainable crop production; it depends
on stability of soil aggregation. Aggregation has positive effect on reduction of soil
erosion, soil water storage, increase water infiltration rate and improve other related
soil properties. The soil structural stability was significantly correlated ( r = 0.67 )
with TOC as the organic material plays crucial role for binding and stabilization of
soil aggregates that serves as indicator for improvement of soil properties (Arshad
and Coen 1992). Tillage operation and crop residues management have direct
influence on soil aggregates. Intensive tillage through moldboard breaks the soil
72
Figure 9. Aggregate stability concentration under the tillage treatements with and
without crop residue was not effected by different tillage systems and residues
management.
a
a
a aa
a
a a
20
24
28
32
36
Without residue
With residue
dd
bcbc
bc bc
a a
20
24
28
32
36
Conventional
tillage
Minimum
tillage
Reduced tillage Zero tillage
So
il a
gg
reg
ate
stab
ilit
y (
%)
(a) 2012-13
(b) 2013-14
73
structure and increases losses of organic material while retention of crop residues
helps to enhance organic matter. Mikha and Rice (2004) and Ashagrie et al. (2007)
reported that soil aggregate were susceptible to breakdown by tillage practices. Some
of the other researcher from different studies reported that conservation tillage
systems significantly improve soil aggregate by increasing organic matter contents
(Lopez-Bellido et al., 2010; Muruganandam et al., 2010; Purakayastha et al., 2009).
4.3.2 Surface Cover
The soil surface cover was significantly affected by different tillage systems
(Figure 10a and b). The data for both years (2012-14) showed that surface cover was
65-70% after harvesting previous crop under all the treatments, declined drastically
after mold board ploghing in CT and MT plots at the start of fallow period.
Ploughing with Chisel in RT plots only minutely dispersed surface residues. The
surface cover enormously decreased with each subsequent tillages under CT & MT
and reached to 0% at the end of fallow whereas under RT and ZT slightly decrease
upto 30-32 % was observed.
In conservation tillage systems retention of previous crop residues is an
essential pillar for soil health improvement (CTIC, 2005) while in conventional
systems the intensive mold board ploughing breaks soil residues, enhance its
decomposition. The surface residues cover not only increase organic matter contents
but also interfere all soil properties and as considered a precious commodity (Lal,
2004).
4.3.3 Soil Bulk Density
74
Figure 10. Surface cover under the tillage treatements with and without crop residue
was drastically decreased under intensive tillage systems.
0
20
40
60
80
CT+ MT+
RT+ ZT+
0
20
40
60
80
May Jun July Aug Sep Oct
So
il s
urf
ace
cov
er (
%)
(a) 2012-13
(b) 2013-14
75
Figure 11. Bulk density concentration under the tillage treatements with and without
crop residue was higher under zero tillage with and without crop residues.
bc
bc
b
a
c c
bc
a
1.4
1.45
1.5
1.55
1.6
Without residue
With residue
c
bc
bc
a
c c
bc
a
1.4
1.45
1.5
1.55
1.6
Conventional
tillage
Minimum
tillage
Reduced tillage Zero tillage
Bu
lk d
ensi
ty (
Mg
m-3
)
(a) 2012-13
(b) 2013-14
76
The soil bulk density at wheat sowing in both experimental years was significantly
higher under ZT (Figure 11a and b) than other tillage systems whereas no difference
was observed under RT, MT and CT tillage systems with or without retention of crop
residues. The value observed under ZT was 1.58 Mg m-3 that gradually decreased
with ploughing intensity and thus under RT it was 1.48 Mg m-3, for MT it was 1.45
Mg m-3 and under CT it was 1.44 Mg m-3. The retention of crop residues in all tillage
systems showed a promise for reduction of bulk density but the difference was not
statistically appreciable.
The higher bulk density in ZT plots resulted in a relatively compacted surface
layer. Ploughing with mouldboard under CT and MT as well chisel plough in RT
plots had broken the compacted surface layer which decreased bulk density.
Contrasting results in the literature have been reported about bulk density under
conservation tillage systems. For example Dao (1996) agreed that there was no
significant difference in bulk densities of conservation and conventional tillage
systems, while our result is in line with Mc Vay et al. (2006), Ball-Coelho et al.
(1998) and Schonning & Rasmussen, (2000) who reported that bulk density was high
in starting years of conservation tillage but decreased gradually with time.
4.3.4 Water Infiltration Rate
The data given in figure 12a and b demonstrates that water infiltration into soil
surface was significantly affected by different tillage systems with and without
retention of crop residues. The infiltration rate under CT was 18 cm h-1 followed by
MT and RT both 15 cm h-1 with retention of crop residues. The lower amounts of 7 cm
h-1 water infiltration was observed under ZT plots without retention of crop residues.
77
Figure 12. Infiltration rate under the tillage treatements with and without crop
residue was low under zero tillage without retention of crop residues.
ab
bc
cdd
a ab
ab
bc
0
5
10
15
20
Without residue
With residue
abab
bc
c
a
ab ab
b
5
10
15
20
Conventional
tillage
Minimum
tillage
Reduced tillage Zero tillage
Infi
ltra
tio
n r
ate
(cm
h-1
)
(a) 2012-13
(b) 2013-14
78
The water infiltration under all tillage systems gradually increased with
retention of crop residues. The low intake of water by ZT plots during monsoon was
due to a relatively compacted surface layer that was indicated by higher bulk density
(Figure 13). Ploughing with intensive moldboard in CT and MT plots and chisel
plough in RT plots broke the compacted surface layer that loosened the soil, reduced
bulk density and made inflow of water relatively easier. The result is in line with
Bhattacharyya et al. (2006) and Gicheru et al. (2004) who reported that high bulk
density and low soil porosity have a negative effect on infiltration rates. Guzh (2004)
also reported that there was significantly higher infiltration rate under tilled soil than
untilled soil.
4.3.5 Total Profile Soil Water Cotents
The total profile volumetric soil water contnets upto 90 cm were not
significantly effected by different tillage systems. The water content during fallow
period was numericaly higher under RT plots that was 70 cm m-1 followd by CT
0.68 cm m-1 and MT 0.65 cm m-1 with retention of crop residues whereas lower
value under ZT 0.50 cm m-1 whan residues removed (Figure 13a, b and 14a, b). The
retention of crop residues showed promise for storage of higher moisture contents
than without crop residues.
The reason for higher moisture contents is that ploughing with moldboard in
CT and MT plots and chisel plough in RT had broken the surface compacted layer as
indicated by reduced bulk density also encourged soil water infiltration during
monsoon which ultimately resulted in higher water storage. The retention of crop
79
Figure 13. Volumetric water contents under the tillage treatements with and without
crop residue were remained low under zero tillage without retention of crop residues.
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8Conventional tillageMinimum tillageReduced tillageZero tillage
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr
Vo
lum
etri
c w
ater
co
nte
nts
( c
m m
-1)
(b) 2013-14
(a) 2012-13 Without residues
With residues
80
Figure 14. Volumetric water contents under the tillage treatements with and without
crop residue were remained low under zero tillage without retention of crop residues.
0.2
0.3
0.4
0.5
0.6
0.7
Without residues Conventional tillage
Minimum tillage
Reduced tillage
Zero tillage
0.2
0.3
0.4
0.5
0.6
0.7
May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr
With residues
Vo
lum
etri
c w
ater
co
nte
nts
( c
m m
-1)
(a) 2012-13
(b) 2013-14
81
residues also enhaced storage of water by reducing evaporation losses in ZT and RT
plots as indicated through surface cover while in tilled plots may be due to increase
of organic matter content. The result is in line with Khurshid et al. (2006) and Alam
et al. (2002) who reported that tilled plots stored higher moisture contents due to
lower bulk density and more porosity than the other treatments. In lower depth, the
better results of soil water content under RT are mainly due to break down of sub
surface hard pan (Khurshid et al., 2006). The accumulation of a water reserve below
the surface horizons increases the depth of rooting and improves water availability
for plants, which considerably improves their resistance during periods of drought
(Hong-ling et al., 2008). Wheat roots are mostly found between 0-120 cm depths,
deep ploughing promotes higher water storage in the lower horizons of the soil.
Bonfil et al. (1999) demonstrated that small amounts of water in the subsoil
may be very valuable for profile, principally in dry seasons, which would improve
crop production (Jin et al., 2007; Hongling et al., 2008; Aldea et al., 2005).Water is
the main limiting factor in rainfed areas and profile stored water under lower depth is
valuable during the most sensitive stages of water deficit (Passioura, 1983).
However, the availability of water in the soil profile may be variable for each tillage
system (Lafond et al., 1994). The crop residue left on the soil surface not only
increases organic matter but also reduces evaporation loss and improves soil physical
properties (Unger, 1994; Shaver et al., 2003).
4.3.6 Soil Temperature
The monthly soil temperature during experimental period was not effect
82
Table 4: Effects of different tillage practices with & without crop residue
retentions on soil temperature
Soil Temperature (oC)
2012-13 CT- CT+ MT- MT+ RT- RT+ ZT- ZT+
May 32 30 33 31 32 30 33 31
Jun 37 34 36 35 37 36 37 35
July 33 32 33 32 34 33 35 33
Aug 30 30 30 31 33 31 35 33
Sep 27 27 27 27 29 28 29 30
Oct 24 25 25 25 27 26 28 27
Nov 23 23 23 23 23 24 24 24
Dec 16 17 17 17 17 17 16 17
Jan 13 13 14 14 14 16 14 16
Feb 14 14 13 13 14 15 13 14
Mar 18 19 18 18 18 19 17 17
Apr 26 26 26 26 26 26 25 25
2013-14
May 32 31 33 31 32 30 30 33
Jun 34 33 34 32 33 32 34 30
July 32 30 32 31 32 31 29 33
Aug 31 30 31 30 30 31 31 28
Sep 30 30 30 30 31 30 29 32
Oct 29 29 30 29 32 29 29 32
Nov 20 20 20 20 22 24 21 24
Dec 14 15 14 16 14 16 15 17
Jan 11 11 11 12 12 13 12 14
Feb 11 12 11 14 12 15 12 14
Mar 13 15 13 14 13 14 12 13
Apr 21 21 21 21 22 23 20 22
83
by different tillage systems and residue management (Table 4).
There was a minute variation of soil temperature under different tillage
systems during fallow period without retention of crop residues but during cropping
season the soil temperature remained stable. During summer season soil temperature
was low under different tillage systems with retention of crop residues while during
winter season the soil temperature remained higher under these treatments. The crop
residues maintained stable soil temperature while higher fluctuation of soil
temperature was observed under tillage systems without retention of crop residues.
The crop residue served as surface cover which has a lower heat conductivity and
higher reflection of heat than soil without surface cover and finally it helped to
reduce soil temperature during summer season. Horton et al. (1996) also reported
that straw mulch reduce the soil temperature during warmer season. During winter
season the input of solar energy is low which result in decrease of soil temperature
while surface crop residues and canopy of crop helped to protect the loss of heat
under soil profile and maintained warmer soil temperature during colder season.
Olasantan (1999) and Fabrizzi et al. (2005) also observed that soil temperature is
lower under wheat straw mulch during warmer season and high during colder season.
4.4 WHEAT CROP YIELD AND ECONOMICS
4.4.1 Seedling Emergence
Seedling emergence was significantly affected by different tillage systems
with and without retention of crop residues. In both years the seedling emergence
Figure 15a and b was significantly higher under CT followed by MT and RT with
84
Figure 15. Seedling emergence under the tillage treatements with and without crop
residue was low under zero tillage without retention of crop residues.
ab ab
ab
b
a aab
ab
20
40
60
80
100Without residue
With residue
abab
ab
c
aab
ab
bc
20
40
60
80
100
Conventional
tillage
Minimum
tillage
Reduced tillage Zero tillage
See
dli
ng
em
erg
ence
(p
lan
t m
-2)
(a) 2012-13
(b) 2013-14
85
and without retention of crop residues. The seedling emergence was low under ZT in
both years (56 and 54 plant m-2) without retention of crop residues as well as with
retention of crop residues (58 and 56 plant m-2).
Seedling emergence is the important parameter for crop establishment and
ultimately contributes to crop biomass and yield. The higher seedling emergence in
tilled plots may be related to higher moisture storage during fallow period, reduction
in bulk density and pulverized soil that provide a favorable condition for crop
germination while in ZT plot there was a compacted layer on soil surface during crop
sowing and establishment. Chiroma et al., (2006) and Thomas et al. (2007) reported
improved seedling emergence due to adequate and proper water availability. There is
dire need to improve germination under zero tillage treatments.
4.4.2 Crop Biomass
The Figure 16a demonstrates that crop biomass in 2012-13 was numerically
higher under CT 6.02 Mg h-1 followed by MT 5.92 Mg h-1 and RT 5.9 Mg h-1 with
retention of crop residues while lower values were observed under ZT 4.33 Mg h-1
without retention of crop residues. The same trend was also observed during the year
2013-14 (Figure 16b), that wheat crop biomass was significantly higher under CT
with retention of crop residues. In both experimental years the trend under different
tillage systems was CT> MT> RT> ZT with and without retention of crop residues.
The retention of crop residues also helped to increase biomass than without retention
of crop residues under different tillage systems. The better biomass yield
86
Figure 16. Wheat biomass under the tillage treatements with and without crop
residue was low under zero tillage without retention of crop residues.
a
a
a
aa a
a
4
4.5
5
5.5
6
6.5Without residue
With residue
aa
a
b
aa
a
a
4
4.5
5
5.5
6
6.5
Conventional
tillage
Minimum
tillage
Reduced tillage Zero tillage
Wh
eat
bio
mas
s (M
g h
a-1
)
(a)2012-13
(b) 2013-14
87
during both years under CT is due to higher water content at wheat sowing and
loosening of surface soil due to intensive ploughing that resulted in better seed-soil
contact and hence germination. The intensive ploughing also loosened the soil which
may have helped the roots to penetrate deeper and extract more water and nutrients.
Gill et al. (2000) also conducted a tillage experiment in same region and concluded
that mouldboard plough loosen the soil which help to increase crop biomass. The ZT
plots had lower water content as well as a relatively compact surface layer that not
only reduced seed germination but also hindered root penetration at initial crop
stages.
4.4.3 Grain Yield
Wheat grain yield was also significantly affected by different tillage systems
with and without retention of crop residues. In 2012-13 (Figure 17a) grain yield was
significantly higher under CT 3.26 Mg h-1 followed by MT 3.21 Mg h-1 and RT 3.12
Mg h-1 then by ZT 2.58 Mg h-1 with retention of crop residues. Lower values were
observed under ZT 2.46 Mg h-1 without retention of crop residues. The same
tendency during 2013-14 (Figure 17b) was also noted i.e. CT>MT>RT>ZT. The
yield was low under ZT without retention of crop residues. In all tillage systems
retention of crop residues showed pronounced effect on grain yield than no residue
especially in CT, MT and RT plots.
In CT, MT and RT plots the higher grain yield was also due to higher water
infiltration, enough residual moisture stored during fallow period, seed bed
preparation which reduced bulk density and provided better condition for initial crop
germination and development that led to establishment of a bumper crop and
88
Figure 17. Wheat grain yield under the tillage treatements with and without crop
residue was low under zero tillage without retention of crop residues.
ab abab
c
a ab ab
bc
1
1.5
2
2.5
3
3.5
4
Without residue
With residue
a aa
c
a a a
b
1
1.5
2
2.5
3
3.5
4
Conventional
tillage
Minimum
tillage
Reduced tillage Zero tillage
Wh
eat
gra
in y
ield
(M
g h
a-1
) (a) 2012-13
(b) 2013-14
89
ultimately increased crop yield. Also in RT plots the higher grain yield may be
attributed to breaking of sub-surface hard pan by chisel plough which enhanced
higher water penetration in lower depth during fallow period that encouraged root
development and thus helped for better crop establishment. In ZT plots the lower
grain yield was related to inferior crop establishment due to poor initial crop
germination. The retention of crop residues also showed promising effect to
increased wheat yield than without retention of crop residues. The decrease of crop
yield in ZT plots may be related to delay in initial crop germination. In ZT plots
there was surface compacted layer that may had affected the crop germination and
establishment which ultimately decreased crop yield. Radford et al. (2001) and
Gemtos & Lellis (1997) also reported that late germination decreased crop yield. The
compacted top layer also restricts root development (Whalley et al., 1995).
4.4.4 Harvest Index
Harvest index was also affected by different tillage systems with and without
retention of crop residues during first experimental year. The harvest index value was
similar under CT, MT and RT with retention of crop residues but low under ZT
without residue retention. In 2nd experimental years during 2013-14 the trend
remained same Figure 18b under different tillage system. The HI was higher without
retention of crop residues.
The HI was low under ZT with and without retention of crop residues. Lauver
(2007) founded no significant effect of different tillage systems on harvest index.
90
Figure 18. Wheat crop harvest index under the tillage treatements with and without
crop residue was not effected by different tillage systems and residues management.
0
15
30
45
60
75
Without residue
With residue
0
15
30
45
60
75
Conventional
tillage
Minimum
tillage
Reduced tillage Zero tillage
Har
ves
t In
dex
(a) 2012-13
(b) 2013-14
91
Ahadiyat and Ranamukhaarachchi, (2008) observed that harvest index was higher
under conventional tillage than conservation tillage systems.
4.4.5 Gross margin and efficiency coefficient
The result of gross marginal return (Figure 19a) illustrate that during 2012-13
highest GM return was recorded under RT (Rs. 109375) followed by MT (Rs.
101800) and CT (Rs. 97840) with retention of crop residues while least GM was
recorded under ZT (Rs. 44975) without retention of crop residues. The trend
remained same (Figure 18b) during 2013-14 in 2nd experimental year where RT (Rs.
100380) remained higher followed by MT (Rs. 89590) and CT (Rs. 81990). The
lower amounts of GM (Rs. 41400) were observed under ZT.
In order to decide on tillage systems with best economic return per
investment, efficiency coefficients were calculated. The efficiency coefficients
(Figure 20a) during 2012-13 were 4.24 for ZT followed by RT (4.13) and MT (3.55)
with retention of crop residues while lower under CT (1.76) without retention of crop
residues. The same trend was also observed (Figure 20b) during 2013-14 i.e. higher
under ZT (3.57), RT (3.45) without retention of crop residues and lower under CT
(1.75) with retention of crop residues. The higher gross marginal return and
efficiency coefficient under RT demonstrate that reduced tillage perform better
economic in comparison with other tillage systems.
Increasing costs of inputs such as fuel, fertilizer and seed have rendered the
dryland farming a profitless business for small landholders. Therefore lowering the
92
Figure 19. Gross marginal return under the tillage treatements with and without crop
residue was low under zero tillage with and without crop residues.
40
60
80
100
120Without residueWith residue
40
60
80
100
120
Conventional
tillage
Minimum
tillage
Reduced tillage Zero tillage
Gro
ss m
arg
ins
(10
00
Rs.
ha
-1)
(a) 2012-13
(b) 2013-14
93
Figure 20. Efficiency coefficient under the tillage treatements with and without crop
residue was higher under reduced tillage and zero tillage with and without crop
residues.
1
2
3
4
5Without residueWith residue
1
2
3
4
5
Conventional
tillage
Minimum tillage Reduced tillage Zero tillage
Eff
icie
ncy
co
effi
cien
t (a) 2012-13
(b) 2013-14
94
input cost of dryland agriculture is need of the time. Arif et al. (2007) report that
conservation tillage was found to be economically more feasible for resource less
farmers and also Ahmad et al. (2007) in the same region reported that conservation
tillage was found to be economically beneficial compared to conventional tillage by
reducing input cost. In Pakistan and India at rice-wheat system Hobbs and Gupta
(2004) reported that zero tillage reduces the cost of production up to $ 60 mostly due
to decreasing fuel cost by 60-80 L per hectare and labor cost. Su et al. (2007; Jin et
al. (2007) have also observed that conservation tillage is economically beneficial.
4.5 CENTURY CARBON VALIDATION AND SIMULATIONS
4.5.1 Total Organic Carbon
The simulated values of TOC were strongly correlated with the observed
values under different tillage systems and residue management treatments as
indicated by the r2 value of 94 (Figure 21). Simulated results of the model illustrate
that the highest TOC value was under ZT followed by RT and then by MT, while CT
showed the least TOC content. The trend is same as found in manually observed
results with order of ZT>RT>MT>CT. Thus the CENTURY carbon model was well
validated because the simulated values were very close to the observed results.
The future scenario of tillage systems without retention of crop residues
(Figure 22a) showed that by the end of this century, TOC will decrease under
conventional tillage systems while minor increase under RT and ZT is expected.
Their simulated values were 12 Mg ha-1 under CT, 14.65 Mg ha-1 under RT and
14.48 Mg ha-1 under ZT. When all tillage systems were simulated with retention of
95
Figure 21. Relationship between simulated and observed total organic carbon under
different tillage systems with and without retention of crop residues.
y = 0.971x
r² = 0.945
8
10
12
14
16
18
8 10 12 14 16 18
Sim
ula
ted t
ota
l org
anic
car
bon (
Mg h
a-1
)
Observed total organic carbon ( Mg ha-1 )
96
Figure 22. Simulated total organic carbon under the tillage treatements with and
without crop residue (a) and (b) from (2015-2105) will gradually increase with
reduction of tillage and retention of crop residues.
10
14
18
22
26Without Residues
Conventional tillage
Minimum tillage
Reduced tillage
Zero tillage
12
16
20
24
28
2015 2030 2045 2060 2075 2090 2105
With Residues
Sim
ula
ted
to
tal
org
anic
car
bo
n (
Mg
ha
-1)
(a)
(b)
97
crop residue (Figure 22b), future simulations showed that TOC will gradually
increase with retention of crop residues in all tillage systems including conventional
tillage systems but the increase will be highest under RT and ZT. The expected
highest values by the end of this century will be 25 Mg ha-1 under RT followed by
23.38 Mg ha-1 under ZT.
The reason for reducing trend of total organic carbon under conventional
tillage systems without retention of crop residues is related to low retention of carbon
sources and their rapid decomposition through intensive moldboard system in soil
(Paustian et al., 2000; Christensen, 1996). Whereas reduced tillage system slowly
mixes and maintains stability of organic material. The crop residue and straw
returned back to soil contribute to gathering of soil organic carbon (Duiker and Lal,
1999; Bierke et al., 2008) while reduction in tillage operations keeps it undisturbed.
The crop residue management in fallow wheat system play important role for long
term sustainability in semi arid region (Manley et al., 2002).
4.5.2 Microbial Biomass Carbon
The simulated and observed values of microbial biomass carbon under
different tillage systems with and without retention of crop residues were
significantly corelated to each other with r2 value 0.91 (Figure 23). The observed and
simulated results were very close to each other bacause their trends were same that
retention of crop residues and reduction of tillage operation increased microbial
biomass carbon.
98
The long term future simulations of different tillage systems without retention
of crop residues (Figure 24a) demonstrate that microbial biomass carbon is expected
to be 0.26 Mg ha-1 under CT, 0.45 Mg ha-1 under RT as well as ZT by the end of this
century. Thus the MBC contents will remain low under CT while mior increase
under alternative tillage systems is expected. The future simulations of different
tillage systems with retention of crop residue (Figure 24b) showed that microbial
biomass carbon will gradually increase under all tillage systems when residue is
retained in order of RT>ZT>MT>CT with predicted values of 1.25 Mg ha-1, 1.17 Mg
ha-1, 0.98 Mg ha-1 and 0.90 Mg ha-1 respectively.
The reason for low microbial biomass carbon under CT is mainly due to non
retention of crop residues as well as repeated ploughing and intensive tillage that
destroys the microbial community while reduced tillage provide better envoiremental
conditions for microbial growth. The higher microbial biomass carbon under
different tillage systems with retention of crop residues is related to increased total
organic carbon in soil. The crop residue is the main source of food for microbial
community (Sarathchandra et al., 2001). Soil microbial biomass carbon have been
proposed as sensitive indicator to soil health improvement as effected by different
tillage systems and crop residues (Nannipieri et al., 2003, Filip et al., 2002). Some
other researcher concluded that increasing carbon input and their low mineralization
process is beneficial for increasing microbial biomass carbon under no-till systems
(Mikanova et al., 2009, Simon et al., 2009). They also reported that conservation
tillage practices enhance soil biological activities. Other workers in Pakistan such as
Shah et al. (2003a), Shafi et al. (2007) and Bakht et al. (2009) also reported that
99
Figure 23. Relationship between simulated and observed microbial biomass carbon
under different tillage systems with and without retention of crop residues
Sim
ula
ted
mic
rob
ial
bio
mas
s ca
rbo
n (
Mg
ha
-1)
y = 0.817x
r² = 0.917
0.2
0.4
0.6
0.8
1
1.2
0.2 0.4 0.6 0.8 1 1.2
Observed microbial biomasscarbon ( Mg ha-1 )
100
Figure 24. Simulated microbial biomass carbon under the tillage treatements with
and without crop residue (a) and (b) from (2015-2105) will gradually increase with
reduction of tillage and retention of crop residues.
0.1
0.3
0.5
0.7
0.9
1.1
1.3
Without Residues Conventional tillage
Minimum tillage
Reduced tillage
Zero tillage
0.1
0.3
0.5
0.7
0.9
1.1
1.3
2015 2030 2045 2060 2075 2090 2105
With Residues
Sim
ula
ted
Mic
rob
ial
Bio
mas
s C
arb
on
(M
g h
a-1
)
(b)
(a)
101
retention of crop residues and increased cropping intensity promote soil microbial
activity.
4.5.3 Particulate Organic Carbon
The data given in Figure 25 demonstrates that there was close relationship
between observed and simulated results under different tillage systems and residue
management practices, having r2 value of 0.84. Both the observed and simulated
results showed that particulate organic carbon was higher under RT and ZT tillage
systems with retention of crop residue. When longterm future simulations were run,
the results (Figure 26a) illustarte that POC is expected to remain low under CT
while it will slightly increase under RT and ZT tillage systems if resiude is not
applied. Their expected values by the end of this century are 3.50 Mg ha-1 under CT,
4.56 Mg ha-1 under RT and 4.38 Mg ha-1 under ZT. The future simulations of tillage
systems with residue return (Figure 26b) demonstrate that POC will gradually
increase under all tillage systems with retention of crop residues in order of
RT>ZT>MT>CT. Their estimated values at the end of century are 14.33 Mg ha-1,
12.46 Mg ha-1, 11.86 Mg ha-1 and 10.88 Mg ha-1 respectively under RT, ZT, MT and
CT.
The particulate organic carbon is particially decomposed previous crop
residue. Despite, its small proportion it has a large effect on structural stability and
nutrient-supply ability of soils for which it is considered a key attribute of soil
quality. Ploughing through intensive tillage breaks the soil aggregates and enhances
decomposition of organic matter where as minimum disturbance in conservation
102
Figure 25. Relationship between simulated and observed particulate organic carbon
under different tillage systems with and without retention of crop residues.
y = 0.892x
r² = 0.842
2
3
4
5
6
2 3 4 5 6
Sim
ula
ted
par
ticu
late
org
anic
car
bon
(M
g h
a-1
)
Observed particulate organic carbon (Mg ha-1)
103
Figure 26. Simulated particulate organic carbon under the tillage treatements with
and without crop residue (a) and (b) from (2015-2105) will gradually increase with
reduction of tillage and retention of crop residues.
2
5
8
11
14
Without Residues Conventional tillage
Minimum tillage
Reduced tillage
Zero tillage
2
5
8
11
14
2015 2030 2045 2060 2075 2090 2105
With Residues
Sim
ula
ted
par
ticu
late
org
anic
car
bon
(M
g h
a-1
)
(a)
(b)
104
tillage systems allows slow decomposion of organic material (Haynes, 2005; Kogel-
Knabner et al., 2008). Some other reseacher such as Cambardella and Elliot (1992)
and Haynes (2005) reported that retention of crop residues with passage of time
could increase particulate organic carbon contents. The POC is important indicator
for soil health improvement especially through soil aggregates. Causarano et al.
(2008) and Franzluebbers and Stuedemann (2002) also reported that conservation
tillage systems can significantly improve soil particulate organic carbon.
4.5.4 Mineral Associated Organic Carbon
The simulated and observed results of mineral associated organic carbon
(Figure 27) were significantly corelated to each other with r2 value of 0.87. In
observed results the MOC contents was not significantly improved under different
tillage systems with and wothout retention of crop residues and same trend was also
observed under simulated results.The long term future simulations regarding
different tillage systems without retention of crop residues (Figure 28a) demonstrate
that MOC will drastically decline under CT while will remain stable under
alternative tillage systems. Their estimated values by the end of century are 8.27 Mg
ha-1 under CT and 9.70 Mg ha-1 under each of RT, ZT and MT tillage systems
without retention of crop residues. When different tillage systems were simulated
with retention of crop residues (Figure 28b) the results show that MOC will slightly
improve under RT with value of 9.75 Mg ha-1 .
The reason for drastic decline in MOC under CT tillage systems without
retention of crop residues is related to the higher decomposition of organic carbon
(a)
105
Figure 27. Relationship between simulated and observed mineral associated carbon
under different tillage systems with and without retention of crop residues.
y = 0.996x
r² = 0.858
4
6
8
10
12
4 6 8 10 12
Sim
ula
ted
min
eral
ass
oci
ated
car
bo
n (
Mg
ha
-1)
Observed mineral associated carbon (Mg ha-1)
106
Figure 28. Simulated mineral associated organic carbon under the tillage treatements,
(a) and (b) with and without crop residue from (2015-2105) will drastically decrease
CT tillage systems without retention of crop residues.
8
8.4
8.8
9.2
9.6
10Without Residues
Conventional tillageMinimum tillageReduced tillageZero tillage
9
9.2
9.4
9.6
9.8
10
2015 2030 2045 2060 2075 2090 2105
With Residues
Sim
ula
ted
par
ticu
late
org
anic
car
bon
(M
g h
a-1
)
Sim
ula
ted
min
eral
ass
oci
ated
car
bo
n (
Mg
ha-1
)
(a)
(b)
107
in active and slow pool which ultimately results in reduction of carbon in passive
pool. The higher contents of MBC and POC under ZT and RT with retention of crop
residues will ultimately lead to increased MOC. The mineral associated organic
carbon materials are more resistant for furher decomposition and are important for
maintaing the quality of soil.
The intnesive tillage practices can reduced soil organic carbon pools inclding
mineral associated carbon. Murty et al. (2002) and Ogle et al. (2003) analyzed 67
longterm experimental soil samples and concluded that intensive tillage resulted in
50% depletion of soil carbon pools. Agricultural management practices including
tillage and crop residues are of great influence on stable soil organic pool. Most of
the researchers aggreed on stable soil organic carbon depletion after convertion from
natural echosystem to aggriculture land (Guo and Gifford 2002). Conservation
agriculture management practices like reduction of tillage operation, retntion of crop
residues and growing of crop with different rotations increase organic input to the
soil and reduce decomposition process that is well known stratagey to increase soil
organic carbon pools (Halvorson et al., 2002; McConkey et al., 2003).
4.5.5 Crop Biomass
The simulated and observed crop biomass under different tillage systems and
residue manamgnet practices (Figure 29) demonstrate significant corelation between
each other having r2 value of 0.81. The initial two years simulated results as well as
manually observed resultus showed that crop biomass is higher under different tillage
systems with retention of crop residus.
108
The future long term prediction of crop biomass under different tillage
systems without retention of crop residues (Figure 30a) demanstare that crop biomass
production will remain similar in the range of 7.75 Mg ha-1 under all tillage systems
without retention of crop residues. The Figure 30b illustrates effect of different
tillage systems with retention of crop residues on biomass production. The trend
showed that biomass will increase with retention of crop residues in all tillage
systems but higher values of 10 Mg ha-1 are expected under alternative tillage
systems of RT and ZT.
The crop bimass production is related to profile water storage and soil organic
matter contents. The tilled plots especially with chisel plough help to increase deep
storage of soil water while retention of crop residues helps to reduce evaporation
losses as well as increase soil organic matter contents which ultimetly increased
water holding capacity of soil. Some of the other researcher such as Li and Shu
(1991) and Musick et al. (1994) reported that increasing soil water contents
especially at sowing time will help to increase crop production.
4.5.6 Grain Yield
The relationship between observed and simulated wheat crop yield is
presented in Figure 31 which demonstrates statistically significant correlation with
value of r2 = 0.77. Figure 32a presents future prediction regarding the effects of
different tillage practices without retention of crop residues on wheat crop yield.The
data shows that expected yield will be minutely higher under RT however in other
tillage systesm it will remain similar.
109
Figure 29. Relationship between simulated and observed biomass yield under
different tillage system with and without retention of crop residues
y = 1.456x - 2.005r² = 0.814
4
5
6
7
8
4 5 6 7 8
Observed biomass yield (Mg ha-1)
Sim
ula
ted
bio
mas
s y
ield
(M
g h
a-1
)
110
Figure 30. Simulated wheat biomass under the tillage treatements with and without crop residue from (2015-2105)
will gradually increase with reduction of tillage and retention of crop residues.
Sim
ula
ted
wh
eat
bio
mas
s (M
g h
a-1
)
111
In case of retention of crop residues in all tillage systems (Figure 32b) it is expected
that wheat grain yield will increase with CT and RT tillage systems.
The future projections show that yield will increase with retention of crop
residues in all tillage systems. The crop residues will help to increase SOC contnets
and thus soil water conservation and nutrient availability. Most of the researchers
agree that in initial 5 years yield under conservation tillage systems is low or equal to
conventional tillage practices but with the passage of time and improving soil
organic carbon the yield will increase (So et al., 2009; Arrúe et al., 2007). It has also
been reported that during drier periods yield is higher under conservation tillage than
conventional tillage (Moreno et al., 1997). These results suggests that crop residues
on soil surface help to reduce soil water evaporation losses and help in better
utilization of soil profile moisture. Crop residue management is an important piller of
conservation tillage systems, with the passage of time the crop residues will
certainely increase organic matterial which ultimetly help in the availabilty of plant
nutrient, enhance water use efficiency and storage of water under soil profile
(Huanget al., 2008).
112
Figure 31. Relationship between simulated and observed grain yield under different
tillage system with and without retention of crop residues
y = 1.042x
r² = 0.769
2
2.4
2.8
3.2
3.6
4
2 2.4 2.8 3.2 3.6 4
Sim
ula
ted
gra
in y
ield
(M
g h
a-1
)
Observed grain yield (Mg ha-1)
113
Figure 32. Simulated wheat grain yield under the tillage treatements with and without crop residue from (2015-2105)
will gradually increase with reduction of tillage and retention of crop residues.
Sim
ula
ted
gra
in y
ield
(M
g h
a-1
)
114
SUMMARY
Conservation tillage systems are being advocated worldwide for sustainable crop
production. However, their effects on soil properties depend on site, climatic
condition and their benefits take longer period to appear. Computer based models
have the ability to simulate long term soil properties under different management
practices. Among these, CENTURY carbon model is widely used to estimate SOC
and crop production. Therefore, a two-year field experiment was conducted at
University Research Farm, Chakwal Road, of PMAS-Arid Agriculture University
Rawalpindi. The objectives of the study were i) to compare conventional and
conservation tillage practices for their effects on biochemical and physical properties
of soil ii) to evaluate conservation tillage system against conventional practices for
wheat yield and economic benefit iii) to validate CENTURY agro ecosystem model
for long term simulation of different soil management practices under agro-climatic
conditions of Pothwar. Treatments were applied in split-plot design, the tillage
practices as main-plot treatments having conventional tillage (CT, moldboard
ploughed at summer start and cultivation after each rainfall), minimum tillage (MT,
moldboard ploughed at start of monsoon, 2 cultivations during fallow, one
cultivation at wheat sowing), reduced tillage (RT, chisel ploughed at the start of
monsoon weed controlled by chemical and wheat sown with zero drill), zero tillage
(ZT, crop was sown with zero tillage drill and summer weeds were controlled
through chemical herbicide). Sub-plot treatments were residue retained (+R) and
removed (-R). The tillage practices were carried out during summer fallow period
and wheat was grown during winter season in all plots.
101
115
All the above mentioned objectives were successfully achieved and
hypotheses were proven to be correct. The soil organic carbon was significantly
improved by ZT and RT with retention of crop residues. The values for MBC, POC,
SOC were 473 µg kg-1, 2.27 g kg-1 and 7.80 g kg-1 under ZT and 425 µg kg-1, 1.94 g
kg-1 and 7.54g kg-1 under RT. Similarly ZT and RT with residue had 37% and 34%
higher water stable aggregates than CT without crop residue retention. As regards
soil physical properties, CT and RT reduced the bulk density, enhanced infiltration
rate and soil profile water content compared with ZT. The seedling emergence,
biomass yield and grain yield were similar under CT, MT and RT whereas ZT had
lower seedling emergence and yields. The gross margins were highest under RT (Rs.
109375) followed by MT (Rs. 101800) and CT (Rs. 97840) all with residue, whereas
ZT without residue gave the lowest gross margin of Rs. 7187. The efficiency
coefficient that shows the return per investment was highest under ZT (4.13) and RT
(4.24). The initial two years model result strongly correlate with actual results with
the r2 values of 0.93 for TOC, 0.87 for MBC, 0.85 for POC and 0.87 for MOC.
Similarly r2 values for biomass and grain yields were 0.76 and 0.81 respectively.
Long term future simulations demonstrated that SOC can gradually increase under all
tillage systems if crop residue is retained whereas CT without retention of crop
residue can drastically reduce the SOC especially the MOC. The simulations also
showed that yield and crop biomass can increase by residue retention in all tillage
systems. The study concludes that conservation tillage practices especially the
reduced tillage (chiseling) and retention of crop residues has potential to improve soil
organic carbon, structural stability, nutrient availability and economic benefits while
providing sufficient yield in dryland Pothwar, Pakistan.
116
Conclusion
Our results confirm that long term adoption of reduced tillage (chiseling) and
retention of crop residues enhances surface soil organic carbon, structural stability,
nutrient availability and crop yield while conventional tillage system through
moldboard plough without retention of crop residues disturbs soil structure, reduces
SOC contents and increases input cost. We conclude that conservation tillage
practices especially the reduced tillage (chiseling) and retention of crop residues has
potential to improve soil quality and economic benefits for farmers while providing
sufficient crop yield in dryland Pothwar, Pakistan. We further suggest that in future,
experiments on conservation tillage should be long-term, multi-location and
multidisciplinary involving agricultural engineers, plant pathologists, and plant
breeders to draw clearer conclusions regarding conservation tillage in dry land areas
of Pakistan.
117
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APPENDICES
Annex 1: ANOVA Total organic carbon over tillage practices and crop residues
2013 2014
SOV DF F p ≥F F p ≥F
Replication (A)
3
Tillage (B) 3 2.10 0.1701 8.75 0.0049
Error A*B 9
Residues (C) 1 5.36 0.0392 71.75 0.0000
B*C 3 0.86 0.4892 2.10 0.1538
Error A*B*C 12
Total 31
CV= 8.92 CV = 10.2
Annex 2: Microbial biomass carbon over tillage practices and crop residues
2013 2014
SOV DF F p ≥F F p ≥F
Replication (A)
3
Tillage (B) 3 12.58 0.0014 40.84 0.0000
Error A*B 9
Residues (C) 1 47.35 0.0000 15.27 0.0021
B*C 3 0.86 0.4905 0.89 0.4754
Error A*B*C 12
Total 31
CV= 13.63 CV = 23.08
131
145
Annex 3: Particulate organic carbon over tillage practices & crop residues
2013 2014
SOV DF F p ≥F F p ≥F
Replication (A)
3
Tillage (B) 3 6.92 0.0103 23.40 0.0001
Error A*B 9
Residues (C) 1 5.50 0.0371 37.38 0.0001
B*C 3 0.63 0.6089 4.69 0.0217
Error A*B*C 12
Total 31
CV= 13.44 CV = 9.47
Annex 4: Mineral associated carbon over tillage practices and crop residue
2013 2014
SOV DF F p ≥F F p ≥F
Replication (A)
3
Tillage (B) 3 0.18 0.9074 0.20 0.8908
Error A*B 9
Residues (C) 1 4.35 0.0591 6.82 0.0227
B*C 3 0.38 0.7687 0.07 0.9771
Error A*B*C 12
Total 31
CV= 5.67 CV = 8.40
146
Annex 5: Nitrate-N over tillage practices and crop residues
2013 2014
SOV DF F p ≥F F p ≥F
Replication (A)
3
Tillage (B) 3 0.04 0.9875 3.73 0.0543
Error A*B 9
Residues (C) 1 0.06 0.8144 26.11 0.0003
B*C 3 0.01 0.9983 4.87 0.0193
Error A*B*C 12
Total 31
CV= 13.58 CV = 8.65
Annex 6: Available phosphorus over tillage practices and crop residues
2013 2014
SOV DF F p ≥F F p ≥F
Replication (A)
3
Tillage (B) 3 0.03 0.9926 15.19 0.0007
Error A*B 9
Residues (C) 1 0.86 0.3730 15.68 0.0019
B*C 3 0.02 0.9946 1.74 0.9946
Error A*B*C 12
Total 31
CV= 13.58 CV = 10.91
147
Annex 7: Extractable potassium over tillage practices and crop residues
2013 2014
SOV DF F p ≥F F p ≥F
Replication (A)
3
Tillage (B) 3 0.16 0.9218 0.13 0.9379
Error A*B 9
Residues (C) 1 0.10 0.7546 2.17 0.1661
B*C 3 0.20 0.8973 0.03 0.9930
Error A*B*C 12
Total 31
CV= 9.45 CV = 21.23
Annex 8: Structural stability over tillage practices and crop residues
2013 2014
SOV DF F p ≥F F p ≥F
Replication (A)
3
Tillage (B) 3 15.82 0.0006 16.25 0.0006
Error A*B 9
Residues (C) 1 13.56 0.0031 49.96 0.0031
B*C 3 0.23 0.8768 0.19 0.8768
Error A*B*C 12
Total 31
CV= 8.76 CV = 7.00
148
Annex 9: Soil surface cover over tillage practices and crop residues
May-12 Jun-12
SOV DF F p ≥F F p ≥F
Replication
3
Tillage 3 0.11 0.9549 0.10 0.9573
Error 9
Total 15
CV= 14.08 CV = 9.16
July-12 Aug-12
SOV DF F p ≥F F p ≥F
Replication
3
Tillage 3 67.74 0.0000 344.42 0.0000
Error 9
Total 15
CV= 15.08 CV = 8.96
Sep-12 Oct-12
SOV DF F p ≥F F p ≥F
Replication
3
Tillage 3 176.28 0.0000 426.91 0.0000
Error 9
Total 15
CV= 16.14
CV = 10.51
149
May-13 Jun-13
SOV DF F p ≥F F p ≥F
Replication
3
Tillage 3 0.75 0.5482 0.92 0.4674
Error 9
Total 15
CV= 7.46 CV = 6.33
July-13 Aug-13
SOV DF F p ≥F F p ≥F
Replication
3
Tillage 3 120.52 0.0000 98.27 0.0000
Error 9
Total 15
CV= 13.28 CV = 17.63
Sep-13 Oct-13
SOV DF F p ≥F F p ≥F
Replication
3
Tillage 3 123.56 0.0000 127.35 0.0000
Error 9
Total 15
CV= 18.15 CV = 19.75
150
Annex 10: Bulk density over tillage practices and crop residues
2013 2014
SOV DF F p ≥F F p ≥F
Replication (A)
3
Tillage (B) 3 1.33 0.3248 1.31 0.3304
Error A*B 9
Residues (C) 1 0.98 0.3420 0.35 0.5678
B*C 3 0.05 0.9853 0.04 0.9877
Error A*B*C 12
Total 31
CV= 6.72 CV = 6.21
Annex 11: Infiltration rate over tillage practices and crop residues
Monsoon, 2012 Monsoon, 2013
SOV DF F p ≥F F p ≥F
Replication (A)
3
Tillage (B) 3 7.73 0.0073 2.70 0.1086
Error A*B 9
Residues (C) 1 0.56 0.4693 7.53 0.0178
B*C 3 0.02 0.9956 0.08 0.9700
Error A*B*C 12
Total 31
CV= 13.44 CV = 17.086
151
Annex 12: Seedling emergence over tillage practices and crop residues
2012 2013
SOV DF F p ≥F F p ≥F
Replication (A)
3
Tillage (B) 3 6.01 0.0156 17.62 0.1086
Error A*B 9
Residues (C) 1 3.30 0.0945 0.41 0.41
B*C 3 0.46 0.7148 0.08 0.9865
Error A*B*C 12
Total 31
CV= 5.41 CV = 15.86
Annex 13: Wheat crop biomass tillage practices and crop residues
2013 2014
SOV DF F p ≥F F p ≥F
Replication (A)
3
Tillage (B) 3 1.99 0.1855 7.73 0.0073
Error A*B 9
Residues (C) 1 0.20 0.6639 16.07 0.0017
B*C 3 0.47 0.7087 1.25 0.3339
Error A*B*C 12
Total 31
CV= 6.06 CV = 6.06
152
Annex 14: Wheat grain yield over tillage practices and crop residues
2013 2014
SOV DF F p ≥F F p ≥F
Replication (A)
3
Tillage (B) 3 4.88 0.0279 22.16 0.0002
Error A*B 9
Residues (C) 1 1.99 0.1839 2.72 0.1251
B*C 3 0.08 0.9698 0.90 0.4719
Error A*B*C 12
Total 31
CV= 16.89 CV = 10.60
153
Appendix 27: Correlation coefficient among soil properties and crop production with retention of crop residues.
TOC MBC POC MOC Aggregt Biomass Yield BD Infilt Moist N P K
TOC 1 0.74** 0.68** 0.13 0.67** -0.31 -0.42 0.16 -0.43 -0.21 0.62** 0.64** -0.28
MBC 0.74** 1 0.62** 0.08 0.83** -0.55* -0.54* 0.43 -0.55* 0.008 0.44 0.55* -0.33
POC 0.68** 0.62** 1 0.4 0.65** -0.41 -0.56* 0.24 -0.3 -0.22 0.72 0.72** 0.12
MOC 0.13 0.08 0.4 1 0.09 -0.19 -0.004 0.03 0.24 -0.06 0.14 0.09 0.06
Aggreg 0.67** 0.83** 0.65** 0.09 1 -0.63** -0.62** 0.4 -0.58* -0.16 0.41 0.45 -0.03
Biomass -0.31 -0.55* -0.41 -0.19 -0.63** 1 0.8 -0.33 0.36 0.1 -0.01 -0.18 0.11
Yield -0.42 -0.54* -0.56* -
0.004
-0.62** 0.8** 1 -0.193 0.51 0.26 -0.19 -0.42 0.03
BD 0.16 0.43 0.24 0.03 0.4 -0.33 -0.19 1 -0.33 -0.24 0.005 0.06 -0.31
Infilt -0.43 -0.55* -0.3 0.24 -0.58* 0.36 0.51* -0.33 1 0.53* -0.39 -0.5 0.14
Moist -0.21 0.008 -0.22 -0.06 -0.16 0.1 0.26 -0.24 0.53* 1 -0.4 -0.38 0.06
N 0.62** 0.44 0.72** 0.14 0.41 -0.01 -0.19 0.005 -0.39 -0.4 1 0.78** 0.04
P 0.64** 0.55* 0.72** 0.09 0.45 -0.18 -0.42 0.06 -0.5 -0.38 0.78** 1 -0.03
K -0.28 -0.33 0.12 0.06 -0.03 0.11 0.03 -0.31 0.14 0.06 0.04 -0.03 1
154
Appendix 28: Correlation coefficient between soil properties and crop production without retention of crop residues.
TOC MBC POC MOC Aggreg Biomass Yield BD Infilt Moist N P K
TOC
1 0.17 0.34 0.30 0.52* -0.36 -0.06 0.27 -0.47 0.19 -0.11 0.23 0.41
MBC
0.17 1 0.71** 0.25 0.6** -0.44 -0.55 0.02 -0.77 -0.52 0.08 0.38 0.12
POC
0.34 0.71** 1 0.43 0.67** -0.61** -0.43 0.13 -0.69** -0.32 0.11 0.04 0.06
MOC
0.30 0.25 0.43 1 0.40 -0.25 -0.02 0.15 -0.12 0.05 0.03 -0.03 -0.05
Aggreg
0.52* 0.6* 0.67** 0.40 1 -0.68** -0.50* 0.24 -0.75 -0.49 0.03 0.43 -0.01
Biomass
-0.36 -0.44 -0.61 -0.25 -0.68** 1 0.59* -0.54* 0.63** 0.48 0.08 -0.33 0.22
Yield -0.06 -0.55* -0.43 -0.02 -0.50* 0.59* 1 -0.22 0.70**
0.55* -0.34 -0.24 -0.01
BD
0.27 0.02 0.13 0.15 0.24 -0.54* -0.22 1 -0.39 -0.22 -0.09 -0.007 -0.20
Infilt
-0.47 -0.77** -0.69** -0.12 -0.75** 0.63** 0.70** -0.39 1 0.47 -0.19 -0.40 -0.17
Moist
0.19 -0.52* -0.32 0.05 -0.49 0.48 0.55* -0.22 0.47 1 0.16 -0.53* 0.50*
N
-0.11 0.08 0.11 0.03 0.03 0.08 -0.34 -0.09 -0.19 0.16 1 -0.32 0.16
P
0.23 0.38 0.04 -0.03 0.43 -0.33 -0.24 -0.007 -0.40 -0.53* -0.32 1 -0.20
K
0.41 0.12 0.061* -0.057 -0.01 0.22 -0.01 -0.20 -0.17 0.50* 0.16* -0.20 1
155
Appendix 29: Weather File Appendix (1981-2014)
prec 1981 4.80 3.30 20.10 12.10 4.10 0.60 7.30 17.00 6.20 1.50 0.60 0.90
tmin 1981 -99.99 -99.99 -99.99-99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
tmax 1981 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
prec 1982 3.70 4.35 22.1110.10 3.85 1.40 8.40 19.20 8.10 2.00 1.50 1.10
tmin 1982 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
tmax 1982 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
prec 1983 3.80 10.90 1.80 22.30 6.70 1.60 7.20 9.00 8.80 1.00 0.00 0.00
tmin 1983 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
tmax 1983 -99.99 -99.99 -99.99 99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
prec 1984 0.00 2.50 2.10 1.40 0.30 3.60 15.90 12.90 6.20 0.10 1.20 0.60
tmin 1984 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
tmax 1984 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
prec 1985 0.70 0.30 1.00 2.50 0.70 2.80 6.20 3.90 1.40 1.70 0.10 1.90
tmin 1985 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
tmax 1985 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
prec 1986 0.20 3.50 3.60 2.00 4.50 3.70 4.60 2.00 6.20 1.80 0.90 3.20
tmin 1986 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
tmax 1986 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
prec 1987 0.00 5.60 6.40 2.00 4.70 2.40 5.80 7.70 6.10 1.60 0.00 0.20
tmin 1987 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
tmax 1987 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
prec 1988 0.20 1.70 9.10 0.60 0.80 2.20 1.90 19.90 3.60 0.40 0.00 3.50
tmin 1988 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
tmax 1988 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
prec 1989 2.10 0.70 9.10 1.70 0.80 0.00 11.40 10.10 2.40 0.00 0.00 9.70
tmin 1989 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
tmax 1989 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
prec 1990 1.90 6.50 7.30 1.40 2.50 2.50 11.80 19.60 13.30 1.10 0.00 9.90
156
tmin 1990 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
tmax 1990 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
prec 1991 0.20 5.40 8.50 7.40 3.50 2.50 9.90 13.80 7.40 0.60 2.00 0.50
tmin 1991 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
tmax 1991 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
prec 1992 5.10 5.40 14.20 5.20 6.90 3.90 8.90 17.30 29.10 0.30 1.10 0.40
tmin 1992 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
tmax 1992 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
prec 1993 1.00 1.50 6.0 3.70 3.60 12.40 4.50 15.70 0.00 0.00 0.00 0.00
tmin 1993 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
tmax 1993 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
prec 1994 2.30 1.80 0.90 4.80 2.30 5.20 14.40 16.10 1.60 1.20 0.00 2.40
tmin 1994 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
tmax 1994 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
prec 1995 0.20 3.90 10.80 7.30 0.80 4.70 12.10 21.60 0.70 1.50 0.00 0.40
tmin 1995 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
tmax 1995 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
prec 1996 10.90 5.90 8.60 1.20 1.10 9.70 4.20 20.40 2.70 6.00 0.00 0.30
tmin 1996 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
tmax 1996 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
prec 1997 2.80 0.30 2.50 13.00 7.10 9.90 21.70 44.30 9.70 10.50 1.90 0.40
tmin 1997 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
tmax 1997 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
prec 1998 2.20 15.90 1.70 9.60 2.20 13.30 9.80 21.80 3.60 4.40 0.00 0.00
tmin 1998 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 25.84 24.50 22.09 17.00 7.57 2.45
tmax 1998 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 35.00 34.12 32.85 30.65 26.33 21.50
prec 1999 13.00 1.86 2.23 1.93 1.66 6.45 16.27 13.47 8.76 0.93 1.80 0.00
tmin 1999 5.43 7.06 9.16 14.31 20.87 21.62 0.00 22.40 21.96 14.73 8.68 2.17
tmax 1999 14.59 18.61 23.59 23.18 37.44 38.32 0.00 35.00 33.76 31.20 25.53 22.32
157
prec 2000 6.15 7.30 0.95 1.10 2.30 5.85 19.18 9.33 19.50 0.00 0.00 0.85
tmin 2000 2.89 3.80 7.39 13.02 23.45 24.18 24.20 23.90 21.00 15.90 8.10 3.40
tmax 2000 17.43 17.36 24.32 34.50 41.20 39.28 35.70 36.70 34.70 33.80 26.40 21.50
prec 2001 0.00 0.00 5.25 3.80 2.60 9.85 19.60 12.40 3.90 4.57 0.35 0.00
tmin 2001 0.20 3.90 9.50 15.90 22.50 23.20 23.50 24.24 20.34 15.80 8.00 4.00
tmax 2001 18.60 21.90 27.40 31.30 38.30 35.90 34.07 24.40 33.57 31.74 27.00 21.20
prec 2002 0.00 4.90 3.30 1.30 0.00 10.70 15.55 30.30 12.55 1.71 0.05 0.04
tmin 2002 1.40 4.20 10.20 15.90 19.65 23.20 23.57 21.41 19.60 15.50 8.80 4.50
tmax 2002 19.00 22.00 26.50 31.30 39.30 35.90 39.43 31.62 30.50 30.60 25.30 19.50
prec 2003 0.05 14.50 3.60 2.71 2.50 0.00 10.60 18.78 7.14 3.56 1.32 1.34
tmin 2003 2.03 9.13 10.22 16.14 19.20 24.20 24.40 23.70 22.20 12.80 7.20 3.70
tmax 2003 18.76 19.80 26.50 33.40 35.20 45.10 34.90 33.30 32.00 30.90 24.10 19.10
prec 2004 6.51 1.94 0.92 6.23 2.58 12.63 4.68 16.91 2.38 3.43 0.24 3.04
tmin 2004 4.20 4.90 10.50 16.90 19.70 22.60 24.90 23.30 21.70 13.80 8.60 4.00
tmax 2004 16.50 21.30 30.20 33.60 37.20 36.70 36.90 33.00 35.00 27.80 25.30 19.40
prec 2005 7.74 6.30 7.53 1.01 3.83 6.05 16.67 9.32 8.50 1.40 0.34 0.00
tmin 2005 2.10 5.20 10.60 12.70 17.30 24.20 24.10 23.90 22.40 15.10 6.50 -0.40
tmax 2005 14.60 15.30 23.00 29.90 32.90 39.70 33.80 34.30 33.90 31.20 24.70 20.60
prec 2006 1.43 2.39 5.52 0.84 1.64 13.51 10.86 7.16 5.16 0.00 4.23 3.02
tmin 2006 1.40 7.60 10.50 14.80 23.40 22.60 25.00 24.20 20.70 16.20 10.20 2.92
tmax 2006 16.90 24.30 24.90 33.00 39.70 37.30 34.90 33.20 33.60 31.70 22.60 18.00
prec 2007 0.00 16.60 14.73 0.78 4.61 11.50 7.98 19.81 9.45 0.00 1.60 0.10
tmin 2007 0.30 6.80 9.30 15.50 21.00 23.80 24.00 24.60 21.30 12.30 7.80 2.20
tmax 2007 18.60 18.10 22.80 32.00 35.20 36.30 34.80 34.10 31.90 31.20 25.60 18.40
prec 2008 4.06 2.92 0.29 6.83 1.23 22.56 9.30 16.29 1.08 0.63 0.20 6.85
tmin 2008 -0.60 2.40 10.40 14.40 20.10 22.50 23.40 22.50 8.80 14.80 6.00 2.90
tmax 2008 14.20 18.70 29.30 29.50 35.60 33.80 34.30 33.80 33.30 32.00 26.10 20.60
prec 2009 1.97 3.90 3.98 8.46 3.99 0.56 18.93 7.57 4.00 0.40 0.70 0.00
tmin 2009 2.00 3.90 7.90 12.20 17.90 21.10 22.52 23.02 19.90 12.78 7.13 2.60
158
tmax 2009 18.20 19.90 25.50 29.70 37.20 39.30 36.51 35.82 34.90 32.98 23.00 19.81
prec 2010 19.70 55.00 16.30 6.00 56.10 47.80 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
tmin 2010 2.05 6.29 12.73 16.80 20.03 22.20 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
tmax 2010 17.75 18.01 28.98 34.63 35.96 38.16 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
prec 2011 4.00 87.70 23.00 44.20 35.80 51.50 -99.99 42.80 40.20 -99.99 12.70 0.00
tmin 2011 -0.49 6.56 12.86 13.32 20.95 24.65 -99.99 -99.99 21.64 -99.99 9.11 2.20
tmax 2011 16.11 16.11 24.75 28.03 37.81 38.40 -99.99 -99.99 31.04 -99.99 24.89 19.31
prec 2012 22.10 19.85 4.10 23.05 3.25 14.30 14.30 153.35 84.30 16.30 1.00 28.30
tmin 2012 0.53 1.86 7.33 15.08 18.91 23.06 23.06 24.16 20.64 13.31 6.38 3.25
tmax 2012 13.50 16.82 24.60 26.22 35.96 39.87 39.87 32.43 30.53 27.69 23.65 18.56
prec 2013 1.80 18.97 4.62 4.62 0.06 4.52 36.70 73.07 46.07 6.01 2.43 1.11
tmin 2013 1.50 7.61 10.76 14.99 18.69 23.93 24.66 24.16 22.45 14.75 7.65 3.20
tmax 2013 15.86 16.82 23.99 28.83 37.28 38.68 34.63 32.49 33.93 29.95 23.49 18.60
prec 2014 1.60 4.69 29.15 3.07 10.85 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
tmin 2014 0.65 4.90 7.40 11.50 18.30 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
tmax 2014 16.98 16.30 21.50 28.10 32.30 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99 -99.99
