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Global Change Impacts on RiceWheat Provision and the
Environmental Consequences
Peter Grace
SKM - Australia
Cooperative Research Centre for
Greenhouse Accounting
Rice-Wheat Production Systems
Country
Area
(million ha)
India
10
Bangladesh
0.8
Pakistan
2.2
Nepal
0.5
China
9.7
Trends in Rice Yields
Initial yield (t/ha)
10
8
6
4
2
0
-0.7
-0.5
-0.3
-0.1
0.1
Average yield change (t/ha/yr)
0.3
Trends in Wheat Yields
Initial yield (t/ha)
5
4
3
2
1
0
-0.2
-0.1
0
0.1
Average yield change (t/ha/yr)
0.2
Reasons for Productivity Decline
•
•
•
•
•
•
•
Intensification-inefficient N use
Soil organic matter decline
Inappropriate water management
Soil structural decline
Micro-nutrient deficiencies
Pest and disease build-up
Narrow genetic base
Reasons for Productivity Decline
•
•
•
•
•
•
•
Intensification-inefficient N use
Soil organic matter decline
Inappropriate water management
Soil structural decline
Micro-nutrient deficiencies
Pest and disease build-up
Narrow genetic base
Reasons for Productivity Decline
Intensification-inefficient N use
Soil organic matter decline
Soil structural decline
Inappropriate water management
Nitrogen Distribution in Rice-Wheat
Outputs
Inputs
Fertilizer
Manure
Irrigation
Rain
Plant
Leaching
Gaseous
Soil
Environmental Impacts
• Intensification-inefficient N use
Leaching of nitrates to groundwater
Greenhouse gas production - N2O
Environmental Impacts
• Soil organic matter decline
Greenhouse gas production - CO2 + CH4
Environmental Impacts
• Inappropriate water management
– Irrigation without adequate drainage
– Groundwater rises
Salinity (salt) and sodicity (Na)
Environmental Impacts
• Salinity (salt) and plants
– Root water uptake reduced
– Tolerance varies
• Sodicity
– Decreased microbial activity
– Soils less permeable
•
•
•
•
Waterlogging
Run-off
Erosion
Lower plant available water contents
Environmental Impacts
• Inappropriate water management
– Excessive irrigation
Groundwater depletion
Increased pumping - GHG production - CO2
Groundwater Depletion
District
Fall in water Water table
Ricetable
depth
wheat
1974-1993
1993
% total
(m/yr)
(m)
crop area
Gurgaon
Kurukshetra
MohinderGarh
Panipat
Rewari
-0.3
-0.5
-0.6
-0.3
-0.2
10.8
18.2
31.0
10.4
16.8
39
82.3
13.6
80.7
22.5
Water Use (km3/yr)
South Asia - Water Use
1400
1200
1000
800
600
1995
2000
2010
Time (years)
2025
Environmental Impacts
• Soil structural decline
Waterlogging - GHG production - N2O + CH4
CLIMATE
CHANGE
GHGs
REDUCED
GHGs
IMPACT of climate
variability on current
production systems
MITIGATE
further climate
change
CURRENT
PRODUCTION
SYSTEMS
ADAPT to climate
variability
NEW
PRODUCTION
SYSTEMS
IMPROVED
FOOD
PRODUCTION
Key Conclusions from IPCC TAR WG I
•
•
•
•
•
•
An increase in extreme weather event
Higher maximum temperatures & hot days
Higher minimum temperatures
More intense precipitation events
Increased summer drying and risk of drought
Increased Asian summer monsoon
precipitation variability
Climate Extremes
South Asia Climate - GCM Outputs
2080
2050
2020
% change
Winter
Summer Winter Summer
Winter Summer
Temp
1.6
1.1
3.3
2.2
4.5
3.2
Precip
2.7
2.5
-2.1
6.6
5.3
7.9
Asia - Simulated Rice Yields - ORYZA1
0
+Temp oC
1
2
4
340 ppm
0
-7
-14
-31
1.5 X
CO2
23
12
5
-16
Wheat
• Losses of 1-1.5% yield/day occur with late
planting after end November
• Delay due to inability to sow
– Late harvest of previous crop
– Seedbed preparation
Adaptation to Climate Change
• Depends on region specific climate changes
• Promote flexibility - traditional ecological knowledge
• Avoid stress at critical growth stages
– Adjustment of planting dates
– Change cultivar
Mitigation of Climate Change
•
•
•
•
Amount of residue retained
No and reduced tillage
Reduction in fallow periods
Flood reduction
CLIMATE
CHANGE
GHGs
REDUCED
GHGs
IMPACT of climate
variability on current
production systems
MITIGATE
further climate
change
CURRENT
PRODUCTION
SYSTEMS
ADAPT to climate
variability
NEW
PRODUCTION
SYSTEMS
IMPROVED
FOOD
PRODUCTION
Global Warming Potential of Rice-Wheat
Production Systems
• Standard nomenclature
• CH4 = 20 x CO2
• N2O = 310 x CO2
• CARBON EQUIVALENTS
• CARBON to PRODUCTIVITY RATIO
Rice-Wheat system - long-term trials (20 yr)
System
Control
Trt 1
Trt 2
Trt 3
Trt 8
1
Rice
(t/ha)
3.74
5.02
5.67
5.92
6.41
Wheat
(t/ha)
1.71
3.13
3.97
4.38
4.6
Fodder
(t/ha)
1.86
1.93
2.36
2.32
2.47
N fert/crop
(kg/ha)
0
60
120
180
120
Manure
(t/ha)
0
0
0
0
15
estimated for 0-15 cm based on published measurements in other treatments
SOC
(%)
0.49
0.641
0.84
1.061
1.48
Rice-Wheat system - long-term trials (20 yr)
- remove and/or burn crop residues
Treatment:
Control
Trt 1
Trt 2
Trt 3
Trt 8
GHG Source
CO2: Soil tillage
CO2: Diesel1
N2O: Burning residues
N2O: Manure application2
N2O: N fertilizer application2
N2O: Cereal residues retained2
N2O: N-fixing crops3
CH4: Burning residues
CH4: Rice cultivation4
kg CE5/ha
CPR6
3539
260
0.4
0
0
0
1.1
17
100
3953
0.73
3003
260
0.6
0
2.4
0
1.1
25.3
100
4774
0.59
2288
260
0.6
0
4.7
0
1.4
29.9
100
5510
0.57
1502
260
0.7
0
7.1
0
1.4
31.1
100
6086
0.59
0
260
0.7
3
4.7
0
1.5
34.1
200
8032
0.73
Rice-Wheat system - long-term trials (20 yr)
Treatments
Systems
CE (kg C emitted):
Conventional/retain residues
Conventional/burn residues
No till/retain residues
CPR (kg C emitted/kg grain yield):
Conventional/retain residues
Conventional/burn residues
No till/retain residues
Control
Trt 1
Trt 2
Trt 3
Trt 8
3496
3953
2966
4103
4774
3646
4721
5510
4362
5232
6086
4981
7137
8032
6724
0.64
0.73
0.54
0.50
0.59
0.45
0.49
0.57
0.45
0.51
0.59
0.48
0.64
0.73
0.61
Enhancing Rice-Wheat Provision
-Conclusions
• Improved agronomic management
• New germplasm
• Biodiversity