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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).

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Greenhouse gas emissions and mitigation measures in agroecosystem

Greenhouse Gas Emissions and Mitigation Measures in Agroecosystem

Jianping Guo

(Chinese Academy of Meteorological Sciences)

Presented by Chaodong Zhoufor Jianping Guo

(China Meteorological Administration)


Greenhouse gas emissions and mitigation measures in agroecosystem

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.


Greenhouse gas emissions and mitigation measures in agroecosystem

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


Greenhouse gas emissions and mitigation measures in agroecosystem

INTRODUCTION

CO2, CH4 and N2O are the most important greenhouse gases.


Greenhouse gas emissions and mitigation measures in agroecosystem

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.


Greenhouse gas emissions and mitigation measures in agroecosystem

I. GENERAL EMISSIONS

CO2

CH4

N2O

CO2,CH4, N2OEmissions from Agriculture (Bouwman, 1990)


Greenhouse gas emissions and mitigation measures in agroecosystem

I. GENERAL EMISSIONS

CH4

N2O

12599-20090Gg

70-190Gg

CH4, N2OEmissions from Agriculture in China (ADB-GEF-UNEP,1998)


Greenhouse gas emissions and mitigation measures in agroecosystem

I. GENERAL EMISSIONS

N2O

0.096TgN

N2OEmissions from Farmland in China in 1990 (Song,1996)


Greenhouse gas emissions and mitigation measures in agroecosystem

I. GENERAL EMISSIONS

CH4

17.5±1.9Tg

CH4Emissions from Rice Paddy in China in 1990 (Song,1996)


Greenhouse gas emissions and mitigation measures in agroecosystem

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.


Greenhouse gas emissions and mitigation measures in agroecosystem

II. GREENHOUSE GAS EMISSIONS

IN AGROECOSYSTEMS

  • 1. CH4 Production and Emissions

  • Rice Paddies

  • Factors related to CH4emissions from rice paddies:

    • Field

      • Soil temperature (in the 0-15 cm layer)

      • Soil water content

      • Soil Characteristic


Greenhouse gas emissions and mitigation measures in agroecosystem

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


Greenhouse gas emissions and mitigation measures in agroecosystem

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)


Greenhouse gas emissions and mitigation measures in agroecosystem

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


Greenhouse gas emissions and mitigation measures in agroecosystem

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)


Greenhouse gas emissions and mitigation measures in agroecosystem

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)


Greenhouse gas emissions and mitigation measures in agroecosystem

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-1emissions

    • 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).


Greenhouse gas emissions and mitigation measures in agroecosystem

II. GREENHOUSE GAS EMISSIONS

IN AGROECOSYSTEMS

  • 1. CH4 Production and Emissions

  • Rice Paddies

  • Factors related to CH4 emissions from rice paddies

    • Water regime

    • Withrespect 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)


Greenhouse gas emissions and mitigation measures in agroecosystem

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).


Greenhouse gas emissions and mitigation measures in agroecosystem

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.


Greenhouse gas emissions and mitigation measures in agroecosystem

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


Greenhouse gas emissions and mitigation measures in agroecosystem

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


Greenhouse gas emissions and mitigation measures in agroecosystem

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.


Greenhouse gas emissions and mitigation measures in agroecosystem

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)


Greenhouse gas emissions and mitigation measures in agroecosystem

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)


Greenhouse gas emissions and mitigation measures in agroecosystem

II. GREENHOUSE GAS EMISSIONS

IN AGROECOSYSTEMS

  • 2. N2O Production and Emissions

  • Rice Paddies

    • Paddy soils emit nitrous oxide

    • Main factors that determine N2O emissionsin the paddy

      • field water conditions

      • fertilization practices

      • temperature ( at the maturing stage)


Greenhouse gas emissions and mitigation measures in agroecosystem

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).


Greenhouse gas emissions and mitigation measures in agroecosystem

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.


Greenhouse gas emissions and mitigation measures in agroecosystem

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.


Greenhouse gas emissions and mitigation measures in agroecosystem

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).


Greenhouse gas emissions and mitigation measures in agroecosystem

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


Greenhouse gas emissions and mitigation measures in agroecosystem

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 7.8°C to 11.8°C. (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.


Greenhouse gas emissions and mitigation measures in agroecosystem

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


Greenhouse gas emissions and mitigation measures in agroecosystem

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.


Greenhouse gas emissions and mitigation measures in agroecosystem

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)


Greenhouse gas emissions and mitigation measures in agroecosystem

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).


Greenhouse gas emissions and mitigation measures in agroecosystem

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)


Greenhouse gas emissions and mitigation measures in agroecosystem

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.


Greenhouse gas emissions and mitigation measures in agroecosystem

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- > NH4+ > urea > (NH4)2CO3 > 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.


Greenhouse gas emissions and mitigation measures in agroecosystem

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.


Greenhouse gas emissions and mitigation measures in agroecosystem

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).


Greenhouse gas emissions and mitigation measures in agroecosystem

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


Greenhouse gas emissions and mitigation measures in agroecosystem

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.


Greenhouse gas emissions and mitigation measures in agroecosystem

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.


Greenhouse gas emissions and mitigation measures in agroecosystem

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 .


Greenhouse gas emissions and mitigation measures in agroecosystem

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.


Greenhouse gas emissions and mitigation measures in agroecosystem

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.


Greenhouse gas emissions and mitigation measures in agroecosystem

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).


Greenhouse gas emissions and mitigation measures in agroecosystem

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.


Greenhouse gas emissions and mitigation measures in agroecosystem

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.


Greenhouse gas emissions and mitigation measures in agroecosystem

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


Greenhouse gas emissions and mitigation measures in agroecosystem

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


Greenhouse gas emissions and mitigation measures in agroecosystem

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


Greenhouse gas emissions and mitigation measures in agroecosystem

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.


Greenhouse gas emissions and mitigation measures in agroecosystem

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.


Greenhouse gas emissions and mitigation measures in agroecosystem

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


Greenhouse gas emissions and mitigation measures in agroecosystem

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


Greenhouse gas emissions and mitigation measures in agroecosystem

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


Greenhouse gas emissions and mitigation measures in agroecosystem

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.


Greenhouse gas emissions and mitigation measures in agroecosystem

III. PRACTICES TO MITIGATE GREENHOUSE GAS EMISSIONS IN AGRICULTURE

  • 2. Mitigating N2O emissions

    • Rational irrigationRational 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 fertilizationChanging the type of N fertilizer and the amount applied, as well as a rational use of N fertilizer can reduce the N2O emissions.


Greenhouse gas emissions and mitigation measures in agroecosystem

III. PRACTICES TO MITIGATE GREENHOUSE GAS EMISSIONS IN AGRICULTURE

  • 2. Mitigating N2O emissions

    • Increasing the carbon supplyThe 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 Thehydroquinol, dicyandiamide, benzoic acid, nitropyrimidine can significantly restrain N2O emissions (Tenuta et al., 2000; Brown et al., 2000).

    • Breeding new varieties


Greenhouse gas emissions and mitigation measures in agroecosystem

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".


Greenhouse gas emissions and mitigation measures in agroecosystem

III. PRACTICES TO MITIGATE GREENHOUSE GAS EMISSIONS IN AGRICULTURE

  • 3. Mitigating CO2 emissions

    • Changing land useReducing 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 agroecosystemsUsing 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 .


Greenhouse gas emissions and mitigation measures in agroecosystem

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.


Greenhouse gas emissions and mitigation measures in agroecosystem

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.


Greenhouse gas emissions and mitigation measures in agroecosystem

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.


Greenhouse gas emissions and mitigation measures in agroecosystem

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.


Greenhouse gas emissions and mitigation measures in agroecosystem

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.


Greenhouse gas emissions and mitigation measures in agroecosystem

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.


Greenhouse gas emissions and mitigation measures in agroecosystem

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