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Greenhouse Gas Emissions and Mitigation Measures in Agroecosystem

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CH4 Emissions from Rice Paddy in China in 1990 (Song,1996) CH4. 17.5 1.9Tg. I. GENERAL EMISSIONS ... Paddy soils emit nitrous oxide ... – PowerPoint PPT presentation

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Title: Greenhouse Gas Emissions and Mitigation Measures in Agroecosystem


1
Greenhouse Gas Emissions and Mitigation Measures
in Agroecosystem
Jianping Guo (Chinese Academy of
Meteorological Sciences) Presented by Chaodong
Zhou for Jianping Guo (China Meteorological
Administration)
2
The purpose of this paper is to document the
main production and emission processes of
greenhouse gases in relation to agricultural
production , and to examine the potential for
reducing such emissions.
3
CONTENTS
  • Introduction
  • I. General Emissions
  • II. Greenhouse Gas Emissions In Agroecosystems
  • III. Practices to Mitigate Greenhouse Gas
    Emissions In Agriculture
  • IV. Some Measures Of Greenhouse Gas Mitigation In
    China
  • V. Summary

4
INTRODUCTION
CO2, CH4 and N2O are the most important
greenhouse gases.
5
INTRODUCTION
CO2, CH4 and N2O are the most important
greenhouse gases.
Atmospheric concentrations of CO2, CH4 and N2O
are increasing annually by 0.5 , 1.1 and 0.3
,respectively. If greenhouse gas emissions
continue to increase at the present rate, the
average global temperature will increase by about
1 C by the year 2025, and by 3 C by the end of
this century.
6
I. GENERAL EMISSIONS
CO2
CH4
N2O
CO2,CH4, N2O Emissions from Agriculture (Bouwman,
1990)
7
I. GENERAL EMISSIONS
CH4
N2O
12599-20090Gg
70-190Gg
CH4, N2O Emissions from Agriculture in China
(ADB-GEF-UNEP,1998)
8
I. GENERAL EMISSIONS
N2O
0.096TgN
N2O Emissions from Farmland in China in 1990
(Song,1996)
9
I. GENERAL EMISSIONS
CH4
17.51.9Tg
CH4 Emissions from Rice Paddy in China in 1990
(Song,1996)
10
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 1. CH4 Production and Emissions
  • Rice Paddies
  • CH4 emissions from rice paddy result from three
    processes.
  • A concentration gradient that causes diffusion
    through the soil-water and water-air interfaces.
  • The release of gas bubbles from soil surface to
    the atmosphere.
  • Soil CH4 that enters into the plant through the
    roots is released to the atmosphere through the
    plant stomata.

11
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 1. CH4 Production and Emissions
  • Rice Paddies
  • Factors related to CH4 emissions from rice
    paddies
  • Field
  • Soil temperature (in the 0-15 cm layer)
  • Soil water content
  • Soil Characteristic

12
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 1. CH4 Production and Emissions
  • Rice Paddies
  • Factors related to CH4 emissions from rice
    paddies
  • Fertilization
  • Fertilizer formation
  • Quantity applied
  • Application practices

13
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 1. CH4 Production and Emissions
  • Rice Paddies
  • Factors related to CH4 emissions from rice
    paddies
  • Organic fertilizer
  • Addition of rice straw compost
  • (23 - 30 increase of CH4 emissions)
  • Application of fresh rice straw
  • (162 - 250 increase of CH4 emissions)

14
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 1. CH4 Production and Emissions
  • Rice Paddies
  • Factors related to CH4 emissions from rice
    paddies
  • Rice variety

Rice varieties and CH4 emission
15
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 1. CH4 Production and Emissions
  • Rice Paddies
  • Factors related to CH4 emissions from rice
    paddies
  • Plant growth stage.
  • Differences of CH4 emissions at different growth
    periods are significant. 78 of the emissions
    occurs at the reproduction stage. (Shangguan,
    1993)

16
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 1. CH4 Production and Emissions
  • Rice Paddies
  • Factors related to CH4 emissions from rice
    paddies
  • Cultivated practices (Ko et al 2000)

17
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 1. CH4 Production and Emissions
  • Rice Paddies
  • Factors related to CH4 emissions from rice
    paddies
  • Plowing
  • Following spring plowing 42.0 g CH4 m-2
    season-1 emissions
  • Following fall plowing 31.3 g CH4 m-2 season-1
    emissions
  • The increase of CH4 emissions for the field
    plowed in the spring is due to the degradation of
    organic matter during the winter. (Ko et al,
    2000).

18
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 1. CH4 Production and Emissions
  • Rice Paddies
  • Factors related to CH4 emissions from rice
    paddies
  • Water regime
  • With respect to permanent flooding during the
    dry season
  • Intermittent irrigation 15 emission reduction
    (Adhya et al., 2000)
  • Mid-season drainage 43 emission reduction
    (Corton et al, 2000)

19
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 1. CH4 Production and Emissions
  • Rice Paddies
  • Factors related to CH4 emissions from rice
    paddies
  • Water regime
  • In China
  • - Continuous flooding 6.4-12.0 Tg C/yr
  • - Mid-season drainage 1.7-7.8 Tg C/yr
  • a decrease of about 5 Tg C/yr with mid-season
    drainage (Li et al, 2002).

20
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
1. CH4 Production and Emissions Dryland
ecosystems Because methanogenic bacteria are not
active under dry soil conditions, CH4 emissions
are generally small. Furthermore, dryland soils
can absorb CH4 to some extent. Therefore, the
contribution of dryland farming to methane
production and emissions is negligible. But the
normal digestive processes of animals is very
important to CH4 emissions in dryland ecosystems.
21
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 1. CH4 Production and Emissions
  • Dryland ecosystems
  • CH4 emissions from the normal digestive
    processes of animals
  • - Ruminant animals are the major emitters of
    methane
  • - Non-ruminant domesticated animals also
    produce methane

22
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 1. CH4 Production and Emissions
  • Dryland ecosystems
  • The type of digestive system is a major factor.
  • Ruminant animals have the highest methane
    emissions among all animal types. Because the
    capacity of the large intestine to produce
    methane is lower, non-ruminant domesticated
    animals have significantly lower methane
    emissions on a per-animal basis than ruminants

23
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 1. CH4 Production and Emissions
  • Dryland ecosystems
  • The animal's feed intake also affects methane
    emissions.
  • In general, a higher feed intake leads to higher
    methane emissions. Feed intake is positively
    related to animal size, growth rate, and
    production. Therefore, feed intake varies among
    animal types as well as among different
    management practices for individual animal types.

24
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 1. CH4 Production and Emissions
  • Dryland ecosystems
  • Methane emissions from Chinese ruminants

Total CH4 emissions from ruminants in China (Gg)
(Dong, et al., 1996)
25
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 1. CH4 Production and Emissions
  • Dryland ecosystems
  • The management of livestock manure is also a
    source of methane emissions

CH4 emission from livestock and poultry manure
in China (Gg) (Dong, et al., 1996)
26
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 2. N2O Production and Emissions
  • Rice Paddies
  • Paddy soils emit nitrous oxide
  • Main factors that determine N2O emissions in the
    paddy
  • field water conditions
  • fertilization practices
  • temperature ( at the maturing stage)

27
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 2. N2O Production and Emissions
  • Rice Paddies
  • Paddy soils emit nitrous oxide
  • N2O production results from the nitrification and
    denitrification processes by soil bacteria.
    Changes in the soil water content can directly
    impact nitrification and denitrification rates,
    and thus impact on the N2O production.
  • N2O production occurs mainly in the spring under
    anaerobic conditions. Soil ventilation and
    anaerobic conditions can increase N2O production
    and emissions. Poor ventilation of the soil is
    unfavorable to N2O emissions. (Li et al, 2003).

28
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 2. N2O Production and Emissions
  • Rice Paddies
  • There is a negative relationship between N2O and
    CH4 emissions
  • During the early period of field flooding and
    during the dry spell after rice maturing, large
    amounts of N2O are released, whereas little CH4
    is emitted from the rice paddy. During the
    flooding period of rice growth, rice paddy emits
    almost no N2O but large amounts of CH4 (Huang et
    al., 1999).
  • Intermittent irrigation can accelerate N2O
    emissions, but will significantly reduce CH4
    ones.

29
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 2. N2O Production and Emissions
  • Dryland ecosystems
  • Nitrous oxide emissions are significant in
    dryland ecosystems
  • Under weak to moderate anaerobic conditions, the
    nitrification and denitrification processes in
    the soil can produce and release N2O.

30
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 2. N2O Production and Emissions
  • Dryland ecosystems
  • Nitrous oxide emissions are significant in
    dryland ecosystems

90 atmospheric N2O originates from the soil
(Feng et al., 1995).
31
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 2. N2O Production and Emissions
  • Dryland ecosystems
  • The soil environmental factors are susceptible
    to affect N2O production and emissions.
  • - Soil temperature
  • - Soil moisture

32
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 2. N2O Production and Emissions
  • Dryland ecosystems
  • The soil environmental factors are susceptible
    to affect N2O production and emissions.
  • A close and direct relationship between soil N2O
    emissions and air temperature variations was
    found.
  • (N2O emissions increased by 70 when the mean
    annual air temperature increased from 7.8C to
    11.8C. (Khalil, et al, 1990) )
  • Rainfall has a most important impact on the N2O
    flux on the second day following precipitation
    after that, the flux return progressively to
    normal.

33
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 2. N2O Production and Emissions
  • Dryland ecosystems
  • The human activities become the most important
    factor determining the N2O emissions.
  • - Nature of the crop (type and growth stage)
  • - Fertilization (including type, particle
    size and amount of fertilizer, application
    practices)
  • - Irrigation

34
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 2. N2O Production and Emissions
  • Dryland ecosystems
  • The human activities become the most important
    factor determining the N2O emissions.
  • - Nature of the crop (type and growth stage)
  • N2O emissions from corn are the largest among the
    corn, soybean and wheat crops.

35
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 2. N2O Production and Emissions
  • Dryland ecosystems
  • The human activities become the most important
    factor determining the N2O emissions.
  • - Nature of the crop (type and growth stage)

N2O emissions from various plant organs are
contrasting. (Yan et al., 2000)
µg/(FW g d)
36
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 2. N2O Production and Emissions
  • Dryland ecosystems
  • The human activities become the most important
    factor determining the N2O emissions.
  • - Nature of the crop (type and growth stage)
  • N2O emissions by corn occur mainly during the
    growth stage, mainly at the heading/blossoming
    and maturing ones. Following harvest, root
    secretions in the soil are used by nitrification
    and denitrification bacteria, and consequently
    N2O emissions are still continuing (Xu et al.,
    1999a).

37
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 2. N2O Production and Emissions
  • Dryland ecosystems
  • The human activities become the most important
    factor determining the N2O emissions.
  • - Nature of the crop (type and growth stage)

38
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 2. N2O Production and Emissions
  • Dryland ecosystems
  • The human activities become the most important
    factor determining the N2O emissions.
  • - Fertilization
  • The N2O flux above crops is directly related to
    nitrogen sources. The fertilizer use and
    application are the most critical factor
    impacting on N2O emissions. The N fertilizers
    provide basic material to nitrification and
    denitrification bacteria, and contribute to
    increment N2O emissions.

39
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 2. N2O Production and Emissions
  • Dryland ecosystems
  • The human activities become the most important
    factor determining the N2O emissions.
  • - Fertilization
  • The type and amount of fertilizer NO3- gt NH4 gt
    urea gt (NH4)2CO3 gt anhydrous NH3 (Zheng et al.,
    1996).
  • The nitrogen fertilizer particle size N2O
    emissions are positively related to the N
    fertilizer particle size (Cheng et al., 1990).
  • The application methods the use of organic
    fertilizer and the surface application of the
    chemical fertilizer decreased significantly the
    N2O emissions.

40
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 2. N2O Production and Emissions
  • Dryland ecosystems
  • The human activities become the most important
    factor determining the N2O emissions.
  • - Irrigation
  • Irrigation modifies the soil physical
    characteristics, and thereby impacts on the N2O
    flux.
  • The impact of irrigation on N2O production and
    emission occurs mainly through its effect on soil
    water content.

41
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 2. N2O Production and Emissions
  • Dryland ecosystems
  • The human activities become the most important
    factor determining the N2O emissions.
  • - Irrigation
  • Dry climatic conditions and low soil water
    nitrification process.
  • High soil water content, e.g. after rainfall
    denitrification process.
  • Moderate soil water content to the same extent
    by nitrification and denitrification processes

  • (Huang et al, 1999).

42
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 2. N2O Production and Emissions
  • Dryland ecosystems
  • The human activities become the most important
    factor determining the N2O emissions.
  • - Irrigation

N2O Emission
(Zheng et al, 1999).
Soil water content
415g.kg-1
43
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 2. N2O Production and Emissions
  • Dryland ecosystems
  • The management of livestock manure can also
    produce N2O emissions.
  • Nitrous oxide is produced as part of the nitrogen
    cycle through the nitrification and
    denitrification of the organic nitrogen in
    livestock manure and urine. But any useful
    information about nitrous oxide related to animal
    production (or manure) was not be found in China.

44
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 3. CO2 Production and Emissions
  • Dryland ecosystems
  • There are daily variations and seasonal changes
    of atmospheric CO2 concentration in dry farmland
    ecosystems and the vertical gradient of CO2
    concentration above the crop.

45
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 3. CO2 Production and Emissions
  • Dryland ecosystems
  • CO2 flux in the field
  • - in winter wheat field 100-280 mg/(m2.h)
  • - application of urea fertilizer 120-400
    mg/(m2.h)
  • The application of urea fertilizer increases CO2
    emission significantly in comparison with not
    fertilized wheat field .

46
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 3. CO2 Production and Emissions
  • Dryland ecosystems
  • Agricultural management impacts significantly
    on soil respiration.
  • The soil respiration rate is greater under deep
    tillage and deep plowing than that under minimum
    tillage or no-till practices.
  • Increasing the amount of straw returned to the
    field affects the soil respiration rate in a
    positive way.
  • In China, there was 70 of the original organic
    carbon had lost following deforestation and
    farming for 15 years. (Zheng et al., 1996).
  • It is estimated that changes in land use released
    about 270 Gt CO2 (Huang et al., 1998).
    Deforestation and soil exploitation will increase
    CO2 emissions to some extent.

47
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
4. Use of waste materials in agriculture and
their contribution to greenhouse gas emissions
To a large extent, crop products and straws
are consumed directly by humans and animals
later on, much of these materials is returned to
the environment in the form of waste materials
greenhouse gas emissions to the atmosphere are
taking place at that time through physical,
chemical and biological processes.
48
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 4. Use of waste materials in agriculture and
    their contribution to greenhouse gas emissions
  • It is estimated that about 1/3 of the total N2O
    emissions from agriculture is released by
    animals.
  • The global CH4 emissions from the animal waste
    materials amounts to about 28.42Gt (Gou et al.,
    2000).
  • CH4 emissions by ruminants account for some 84
    of the total emissions by livestock (Laville et
    al, 1999).

49
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 4. Use of waste materials in agriculture and
    their contribution to greenhouse gas emissions
  • Straw returned to the field and use of organic
    fertilizer can also change the soil physical and
    chemical characteristics, thereby impacting on
    the activity of methanogenic, nitrification and
    denitrification bacteria, and thus increase the
    CH4 and N2O emission fluxes.
  • Burning of biological agricultural by-products in
    the developing countries, account for 50 of the
    total biological materials being burned. The
    remaining 50 of crop waste materials are burned
    for fuel and energy production.

50
II. GREENHOUSE GAS EMISSIONS IN
AGROECOSYSTEMS
  • 4. Use of waste materials in agriculture and
    their contribution to greenhouse gas emissions
  • It is estimated that some 8.7 Gt of dry matter
    is burned on an annual basis around the world.

51
III. PRACTICES TO MITIGATE GREENHOUSE GAS
EMISSIONS IN AGRICULTURE
  • Two ways to mitigate greenhouse gas
  • to reduce the existing emission sources
  • to enhance the absorbing capacity of current
    agricultural sinks as well as creating new ones

52
III. PRACTICES TO MITIGATE GREENHOUSE GAS
EMISSIONS IN AGRICULTURE
  • 1. Mitigating CH4 emissions
  • Crop production
  • Changing the environmental factors that
    determine the activity of methanogenic bacteria
    through adequate agricultural management
    practices
  • Water level control intermittent irrigation,
    deep irrigation and constant wetness in the rice
    paddy
  • Fertilizer management substituting a chemical
    for than an organic fertilizer

53
III. PRACTICES TO MITIGATE GREENHOUSE GAS
EMISSIONS IN AGRICULTURE
  • 1. Mitigating CH4 emissions
  • Crop production
  • Changing the environmental factors that
    determine the activity of methanogenic bacteria
    through adequate agricultural management
    practices
  • Rice variety ability of rice to release CH4
  • Use of CH4 inhibitor application of urease,
    hydroquinol and dicyandiamide to the soil

54
III. PRACTICES TO MITIGATE GREENHOUSE GAS
EMISSIONS IN AGRICULTURE
  • 1. Mitigating CH4 emissions
  • B. Animal production
  • Techniques to be applied for reducing CH4
    emissions from ruminants
  • Improving the forage quality and incorporating
    nutrition additive in the forage.
  • Using physical and chemical methods to treat
    straw in order to improve forage nutrition value.

55
III. PRACTICES TO MITIGATE GREENHOUSE GAS
EMISSIONS IN AGRICULTURE
  • 1. Mitigating CH4 emissions
  • B. Animal production
  • Techniques to be applied for reducing CH4
    emissions from ruminants
  • Using growth promoter can reduce CH4 emissions
  • Changing the gene characteristics of the animals,
    improving their productivity, increasing the
    number of twins, decreasing the number of
    reproductive animals, and using bio-techniques to
    change the enteric fermentation.

56
III. PRACTICES TO MITIGATE GREENHOUSE GAS
EMISSIONS IN AGRICULTURE
  • 1. Mitigating CH4 emissions
  • C. Management of agricultural waste
  • Controlling incomplete burning of biological
    material through sustainable management of the
    soil and improving land use
  • Improving productivity of existing agricultural
    land
  • Extending the fallow season and improving the
    productivity of the agricultural land
  • Improving the grassland through better land
    management

57
III. PRACTICES TO MITIGATE GREENHOUSE GAS
EMISSIONS IN AGRICULTURE
  • 1. Mitigating CH4 emissions
  • C. Management of agricultural waste
  • Controlling incomplete burning of biological
    material through sustainable management of the
    soil and improving land use
  • Returning crop waste material directly to the
    field
  • Increasing the amount of energy produced from
    crop waste material
  • Changing annual or seasonal crops on marginal
    land into forest

58
III. PRACTICES TO MITIGATE GREENHOUSE GAS
EMISSIONS IN AGRICULTURE
  • 1. Mitigating CH4 emissions
  • C. Management of agricultural waste
  • Controlling incomplete burning of biological
    material through sustainable management of the
    soil and improving land use
  • Improving the grassland through better land
    management
  • Returning crop waste material directly to the
    field
  • Increasing the amount of energy produced from
    crop waste material

59
III. PRACTICES TO MITIGATE GREENHOUSE GAS
EMISSIONS IN AGRICULTURE
  • 2. Mitigating N2O emissions
  • Because the most significant impact on N2O
    emissions come from irrigation and fertilization,
    N2O emissions can be reduced through soil water
    control and rational fertilization.

60
III. PRACTICES TO MITIGATE GREENHOUSE GAS
EMISSIONS IN AGRICULTURE
  • 2. Mitigating N2O emissions
  • Rational irrigation Rational irrigation
    according to crop physiological characteristics
    at different growth stages is essential. It is
    better to reduce the period of alternate dryness
    and wetness and the field exposure to air,
    thereby restraining N2O production and emissions.
  • Rational fertilization Changing the type of N
    fertilizer and the amount applied, as well as a
    rational use of N fertilizer can reduce the N2O
    emissions.

61
III. PRACTICES TO MITIGATE GREENHOUSE GAS
EMISSIONS IN AGRICULTURE
  • 2. Mitigating N2O emissions
  • Increasing the carbon supply The addition of
    organic carbon will result in insufficient oxygen
    supply and reduce the activity of autotrophic
    nitrification bacteria, and finally impact on N2O
    production and emissions.
  • Use of N2O inhibitor The hydroquinol,
    dicyandiamide, benzoic acid, nitropyrimidine can
    significantly restrain N2O emissions (Tenuta et
    al., 2000 Brown et al., 2000).
  • Breeding new varieties

62
III. PRACTICES TO MITIGATE GREENHOUSE GAS
EMISSIONS IN AGRICULTURE
3. Mitigating CO2 emissions The
methods for mitigating CO2 emissions in
agroecosystems are divided in two sections. One
is addressing the decrease of CO2 emissions from
existing sources, while the other is proposing to
reinforce the absorbing ability of CO2 "sink" as
well as creating new CO2 "sinks".
63
III. PRACTICES TO MITIGATE GREENHOUSE GAS
EMISSIONS IN AGRICULTURE
  • 3. Mitigating CO2 emissions
  • Changing land use Reducing the development of
    waste land Using the existing farming land more
    sustainably returning fallow land to forest,
    grassland and fen system to sustain natural
    ecosystems and the C circulation equilibrium.
  • Improving cropland management and reducing carbon
    separation in agroecosystems Using more organic
    fertilizer returning more straw back to the
    cropland using more perennial crops, and
    covering crops during the winter, reducing
    tillage, reducing the fallow period, and
    transforming barren land to cropland or grassland
    .

64
III. PRACTICES TO MITIGATE GREENHOUSE GAS
EMISSIONS IN AGRICULTURE
  • 3. Mitigating CO2 emissions
  • Bio-fuel production
  • As the bio-fuel results from the assimilation of
    atmospheric CO2, burning of bio-fuel will not
    increase atmospheric CO2. It is more favorable
    to mitigate CO2 emission than burning mineral
    fuel.
  • Regions with high production potential should
    take maximum advantage of fallow land to plant
    trees and other crops as bio-fuel feedstock.

65
IV. SOME MEASURES OF GREENHOUSE GAS MITIGATION IN
CHINA
  • Improving the water management techniques
  • Continuous flooding during the rice
    growing season is changed to mid-season drainage,
    which greatly decreases CH4 emissions.
  • Popularization of rebirth energy technology
  • By the end of 2000, there were about 189
    million energy-saving kitchen ranges, eight
    million door marsh gas pools, and one thousand
    great and middle urine engineering were in
    application. The application of them reduced
    about 15 million tons of CO2 and 210 thousand
    tons of CH4 emission.

66
IV. SOME MEASURES OF GREENHOUSE GAS MITIGATION IN
CHINA
  • Return of farmland to forest or grassland In
    more recent years, trees and grassland have
    substituted for annual crops in the western part
    of China.

67
V. SUMMARY
  • CH4 emissions originate mainly from rice paddy
    fields, and are impacted by soil characteristics,
    e.g. temperature, water content, pH and Eh
    conditions, and also by land and crop management,
    e.g. land use, rice varieties, fertilizer
    application.
  • Rice paddy emits not only CH4, but also N2O.
    However, the N2O emission pattern is quite
    different from the CH4 one. Field water
    conditions and fertilization practices are the
    main factors that determine N2O emissions.

68
V. SUMMARY
  • In a farmland ecosystem, CO2 concentration does
    not increase, because CO2 consumption by
    photosynthesis is greater than CO2 emission
    through crop respiration.
  • The use of waste material in agriculture and
    breeding development contributes also to
    greenhouse gas emissions.
  • In order to mitigate greenhouse gas emissions in
    agricultural production, the most important
    measure is to reduce the existing emission
    sources, and the second one is to enhance the
    absorbing capacity of current agricultural sinks
    as well as creating new ones.

69
V. SUMMARY
  • Because the effects of these measures on the
    different greenhouse gases are different,
    specific practices must be developed and adopted
    for the different gases.

70



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