Global Change Impacts on Rice-Wheat 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

0

2

4

6

8

10

-0.7 -0.5 -0.3 -0.1 0.1 0.3

Average yield change (t/ha/yr)

Init

ial y

ield

(t/

ha

)

Trends in Wheat Yields

0

1

2

3

4

5

-0.2 -0.1 0 0.1 0.2

Average yield change (t/ha/yr)

Init

ial y

ield

(t/

ha

)

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

Fertilizer Manure Irrigation Rain Plant Leaching Gaseous Soil

Inputs Outputs

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 watertable

1974-1993(m/yr)

Water tabledepth1993(m)

Rice-wheat% total

crop area

Gurgaon -0.3 10.8 39Kurukshetra -0.5 18.2 82.3MohinderGarh -0.6 31.0 13.6Panipat -0.3 10.4 80.7Rewari -0.2 16.8 22.5

South Asia - Water Use

600

800

1000

1200

1400

1995 2000 2010 2025

Time (years)

Wat

er U

se (

km3/

yr)

Environmental Impacts

• Soil structural decline

Waterlogging - GHG production - N2O + CH4

CLIMATE CHANGE REDUCED

GHGs

NEW PRODUCTION

SYSTEMS

CURRENT PRODUCTION

SYSTEMS IMPROVED FOOD

PRODUCTION

ADAPT to climate variability

MITIGATE further climate

change

IMPACT of climate variability on current production systems

GHGs

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

2020 2050% change

2080

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 XCO2

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 REDUCED

GHGs

NEW PRODUCTION

SYSTEMS

CURRENT PRODUCTION

SYSTEMS IMPROVED FOOD

PRODUCTION

ADAPT to climate variability

MITIGATE further climate

change

IMPACT of climate variability on current production systems

GHGs

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)

SystemRice(t/ha)

Wheat(t/ha)

Fodder(t/ha)

N fert/crop(kg/ha)

Manure(t/ha)

SOC(%)

Control 3.74 1.71 1.86 0 0 0.49Trt 1 5.02 3.13 1.93 60 0 0.641

Trt 2 5.67 3.97 2.36 120 0 0.84Trt 3 5.92 4.38 2.32 180 0 1.061

Trt 8 6.41 4.6 2.47 120 15 1.481estimated for 0-15 cm based on published measurements in other treatments

Rice-Wheat system - long-term trials (20 yr) - remove and/or burn crop residues

Treatment: Control Trt 1 Trt 2 Trt 3 Trt 8GHG SourceCO2: Soil tillage 3539 3003 2288 1502 0CO2: Diesel1 260 260 260 260 260N2O: Burning residues 0.4 0.6 0.6 0.7 0.7N2O: Manure application2 0 0 0 0 3N2O: N fertilizer application2 0 2.4 4.7 7.1 4.7N2O: Cereal residues retained2 0 0 0 0 0N2O: N-fixing crops3 1.1 1.1 1.4 1.4 1.5CH4: Burning residues 17 25.3 29.9 31.1 34.1CH4: Rice cultivation4 100 100 100 100 200kg CE5/ha 3953 4774 5510 6086 8032CPR6 0.73 0.59 0.57 0.59 0.73

Rice-Wheat system - long-term trials (20 yr)

Treatments Control Trt 1 Trt 2 Trt 3 Trt 8SystemsCE (kg C emitted): Conventional/retain residues 3496 4103 4721 5232 7137 Conventional/burn residues 3953 4774 5510 6086 8032 No till/retain residues 2966 3646 4362 4981 6724CPR (kg C emitted/kg grain yield): Conventional/retain residues 0.64 0.50 0.49 0.51 0.64 Conventional/burn residues 0.73 0.59 0.57 0.59 0.73 No till/retain residues 0.54 0.45 0.45 0.48 0.61

Enhancing Rice-Wheat Provision-Conclusions

• Improved agronomic management• New germplasm• Biodiversity