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 Zhou for Jianping Guo (China Meteorological Administration)

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. 6/13/2021 2

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 6/13/2021 3

INTRODUCTION CO 2, CH 4 and N 2 O are the most important greenhouse gases. 6/13/2021 4

INTRODUCTION CO 2, CH 4 and N 2 O are the most important greenhouse gases. Atmospheric concentrations of CO 2, CH 4 and N 2 O 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. 6/13/2021 5

I. GENERAL EMISSIONS CO 2 CH 4 N 2 O CO 2, CH 4, N 2 O Emissions from Agriculture (Bouwman, 1990) 6/13/2021 6

I. GENERAL EMISSIONS CH 4 12599 -20090 Gg N 2 O 70 -190 Gg CH 4, N 2 O Emissions from Agriculture in China (ADB-GEF-UNEP, 1998) 6/13/2021 7

I. GENERAL EMISSIONS N 2 O 0. 096 Tg. N N 2 O Emissions from Farmland in China in 1990 (Song, 1996) 6/13/2021 8

I. GENERAL EMISSIONS CH 4 17. 5± 1. 9 Tg CH 4 Emissions from Rice Paddy in China in 1990 (Song, 1996) 6/13/2021 9

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 1. CH 4 Production and Emissions Rice Paddies CH 4 emissions from rice paddy result from three processes. Ø A concentration gradient that causes diffusion through the soil-water and water-air interfaces. ØThe release of gas bubbles from soil surface to the atmosphere. ØSoil CH 4 that enters into the plant through the roots is released to the atmosphere through the plant stomata. 6/13/2021 10

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 1. CH 4 Production and Emissions Rice Paddies Factors related to CH 4 emissions from rice paddies : • Field - Soil temperature (in the 0 -15 cm layer) - Soil water content - Soil Characteristic 6/13/2021 11

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 1. CH 4 Production and Emissions Rice Paddies Factors related to CH 4 emissions from rice paddies : • Fertilization - Fertilizer formation - Quantity applied - Application practices 6/13/2021 12

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 1. CH 4 Production and Emissions Rice Paddies Factors related to CH 4 emissions from rice paddies : • Organic fertilizer -Addition of rice straw compost (23 - 30 % increase of CH 4 emissions) -Application of fresh rice straw (162 - 250 % increase of CH 4 emissions) 6/13/2021 13

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 1. CH 4 Production and Emissions Rice Paddies Factors related to CH 4 emissions from rice paddies : • Rice variety Rice varieties and CH 4 emission 6/13/2021 14

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 1. CH 4 Production and Emissions Rice Paddies Factors related to CH 4 emissions from rice paddies : • Plant growth stage. Differences of CH 4 emissions at different growth periods are significant. 78 % of the emissions occurs at the reproduction stage. (Shangguan, 1993) 6/13/2021 15

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 1. CH 4 Production and Emissions Rice Paddies Factors related to CH 4 emissions from rice paddies : • Cultivated practices (Ko et al 2000) TRANSPLANTATION 8 -day-oldseedling 42. 4 g CH 4 m-2 CH 4 EMISSIONS season-1 CH 4 REDUCTION 6/13/2021 - 30 -day-oldseedling Direct seedling on wet soil Direct seedling on dry soil 40. 3 g CH 4 m-2 37. 1 g CH 4 m- 26. 9 g CH 4 2 season-1 m-2 season-1 5% 13% 37% 16

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 1. CH 4 Production and Emissions Rice Paddies Factors related to CH 4 emissions from rice paddies : • Plowing -Following spring plowing: 42. 0 g CH 4 m-2 season-1 emissions - Following fall plowing: 31. 3 g CH 4 m-2 season-1 emissions The increase of CH 4 emissions for the field plowed in the spring is due to the degradation of organic matter during the winter. (Ko et al, 2000). 6/13/2021 17

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 1. CH 4 Production and Emissions Rice Paddies Factors related to CH 4 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) 6/13/2021 18

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 1. CH 4 Production and Emissions Rice Paddies Factors related to CH 4 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). 6/13/2021 19

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 1. CH 4 Production and Emissions Dryland ecosystems Because methanogenic bacteria are not active under dry soil conditions, CH 4 emissions are generally small. Furthermore, dryland soils can absorb CH 4 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 CH 4 emissions in dryland ecosystems. 6/13/2021 20

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 1. CH 4 Production and Emissions Dryland ecosystems • CH 4 emissions from the normal digestive processes of animals - Ruminant animals are the major emitters of methane - Non-ruminant domesticated animals also produce methane 6/13/2021 21

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 1. CH 4 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 6/13/2021 22

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 1. CH 4 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. 6/13/2021 23

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 1. CH 4 Production and Emissions Dryland ecosystems • Methane emissions from Chinese ruminants Livestock Type 1985 1990 % Draft Cattle 2805 3343 57. 7 Buffalo 1102 1211 19. 0 93 153 2. 6 Sheep 408 580 10. 0 Goats 308 477 8. 2 31 27 0. 5 4822 5798 Dairy Cattle Camels Total CH 4 emissions from ruminants in China (Gg) (Dong, et al. , 1996) 6/13/2021 24

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 1. CH 4 Production and Emissions Dryland ecosystems • The management of livestock manure is also a source of methane emissions CH 4 emission from livestock and poultry manure in China (Gg) (Dong, et al. , 1996) Animal type 1970 1980 1990 % Dairy cattle 0. 00 6. 13 23. 69 1. 9 Draft cattle 43. 89 40. 34 60. 41 4. 8 Buffalo 29. 46 33. 15 38. 87 3. 1 Swine 574. 73 831. 92 1027. 55 82. 3 Sheep 9. 09 11. 29 11. 72 0. 9 Goats 7. 86 10. 50 12. 51 1. 0 Horses 11. 28 13. 11 12. 49 1. 0 6. 65 7. 42 10. 40 0. 8 14. 73 51. 48 4. 1 968. 59 1248. 52 Mules/Asses Poultry Total 6/13/2021 682. 95 25

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 2. N 2 O Production and Emissions Rice Paddies • Paddy soils emit nitrous oxide Main factors that determine N 2 O emissions in the paddy - field water conditions - fertilization practices - temperature ( at the maturing stage) 6/13/2021 26

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 2. N 2 O Production and Emissions Rice Paddies • Paddy soils emit nitrous oxide ØN 2 O 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 N 2 O production. Ø N 2 O production occurs mainly in the spring under anaerobic conditions. Soil ventilation and anaerobic conditions can increase N 2 O production and emissions. Poor ventilation of the soil is unfavorable to N 2 O emissions. (Li et al, 2003). 6/13/2021 27

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 2. N 2 O Production and Emissions Rice Paddies • There is a negative relationship between N 2 O and CH 4 emissions ØDuring the early period of field flooding and during the dry spell after rice maturing, large amounts of N 2 O are released, whereas little CH 4 is emitted from the rice paddy. During the flooding period of rice growth, rice paddy emits almost no N 2 O but large amounts of CH 4 (Huang et al. , 1999). ØIntermittent irrigation can accelerate N 2 O emissions, but will significantly reduce CH 4 ones. 6/13/2021 28

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 2. N 2 O 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 N 2 O. 6/13/2021 29

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 2. N 2 O Production and Emissions Dryland ecosystems • Nitrous oxide emissions are significant in dryland ecosystems 90% atmospheric N 2 O originates from the soil (Feng et al. , 1995). 6/13/2021 30

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 2. N 2 O Production and Emissions Dryland ecosystems • The soil environmental factors are susceptible to affect N 2 O production and emissions. - Soil temperature - Soil moisture 6/13/2021 31

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 2. N 2 O Production and Emissions Dryland ecosystems • The soil environmental factors are susceptible to affect N 2 O production and emissions. ØA close and direct relationship between soil N 2 O emissions and air temperature variations was found. (N 2 O emissions increased by 70% when the mean annual air temperature increased from 7. 8°C to 11. 8°C. (Khalil, et al, 1990) ) ØRainfall has a most important impact on the N 2 O flux on the second day following precipitation; after that, the flux return progressively to normal. 6/13/2021 32

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 2. N 2 O Production and Emissions Dryland ecosystems • The human activities become the most important factor determining the N 2 O emissions. - Nature of the crop (type and growth stage) - Fertilization (including type, particle size and amount of fertilizer, application practices) - Irrigation 6/13/2021 33

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 2. N 2 O Production and Emissions Dryland ecosystems • The human activities become the most important factor determining the N 2 O emissions. - Nature of the crop (type and growth stage) N 2 O emissions from corn are the largest among the corn, soybean and wheat crops. 6/13/2021 34

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 2. N 2 O Production and Emissions Dryland ecosystems • The human activities become the most important factor determining the N 2 O emissions. - Nature of the crop (type and growth stage) N 2 O emissions from various plant organs are contrasting. (Yan et al. , 2000) ROOT STALK LEAF SOYBEAN 249. 92 388. 66 103. 48 CORN 199. 58 - - RICE 2. 98 - - μg/(FW g d) 6/13/2021 35

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 2. N 2 O Production and Emissions Dryland ecosystems • The human activities become the most important factor determining the N 2 O emissions. - Nature of the crop (type and growth stage) N 2 O 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 N 2 O emissions are still continuing (Xu et al. , 1999 a). 6/13/2021 36

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 2. N 2 O Production and Emissions Dryland ecosystems • The human activities become the most important factor determining the N 2 O emissions. - Nature of the crop (type and growth stage) 6/13/2021 37

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 2. N 2 O Production and Emissions Dryland ecosystems • The human activities become the most important factor determining the N 2 O emissions. - Fertilization The N 2 O flux above crops is directly related to nitrogen sources. The fertilizer use and application are the most critical factor impacting on N 2 O emissions. The N fertilizers provide basic material to nitrification and denitrification bacteria, and contribute to increment N 2 O emissions. 6/13/2021 38

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 2. N 2 O Production and Emissions Dryland ecosystems • The human activities become the most important factor determining the N 2 O emissions. - Fertilization ØThe type and amount of fertilizer : NO 3 - > NH 4+ > urea > (NH 4)2 CO 3 > anhydrous NH 3 (Zheng et al. , 1996). ØThe nitrogen fertilizer particle size : N 2 O emissions are positively related to the N fertilizer particle size (Cheng et al. , 1990). Ø The application methods: the use of organic fertilizer and the surface application of the chemical fertilizer decreased significantly the N 2 O emissions. 6/13/2021 39

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 2. N 2 O Production and Emissions Dryland ecosystems • The human activities become the most important factor determining the N 2 O emissions. - Irrigation ØIrrigation modifies the soil physical characteristics, and thereby impacts on the N 2 O flux. ØThe impact of irrigation on N 2 O production and emission occurs mainly through its effect on soil water content. 6/13/2021 40

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 2. N 2 O Production and Emissions Dryland ecosystems • The human activities become the most important factor determining the N 2 O emissions. - Irrigation üDry climatic conditions and low soil water: nitrification process. üHigh soil water content, e. g. after rainfall: denitrification process. üModerate soil water content: to the same extent by nitrification and denitrification processes (Huang et al, 1999). 6/13/2021 41

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 2. N 2 O Production and Emissions Dryland ecosystems • The human activities become the most important factor determining the N 2 O emissions. - Irrigation N 2 O Emission (Zheng et al, 1999). 415 g. kg-1 6/13/2021 Soil water content 42

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 2. N 2 O Production and Emissions Dryland ecosystems • The management of livestock manure can also produce N 2 O 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. 6/13/2021 43

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 3. CO 2 Production and Emissions Dryland ecosystems There are daily variations and seasonal changes of atmospheric CO 2 concentration in dry farmland ecosystems and the vertical gradient of CO 2 concentration above the crop. 6/13/2021 44

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 3. CO 2 Production and Emissions Dryland ecosystems • CO 2 flux in the field - in winter wheat field: 100 -280 mg/(m 2. h) - application of urea fertilizer: 120 -400 mg/(m 2. h) The application of urea fertilizer increases CO 2 emission significantly in comparison with not fertilized wheat field. 6/13/2021 45

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 3. CO 2 Production and Emissions Dryland ecosystems • Agricultural management impacts significantly on soil respiration. ØThe soil respiration rate is greater under deep tillage and deep plowing than that under minimum tillage or no-till practices. ØIncreasing the amount of straw returned to the field affects the soil respiration rate in a positive way. ØIn China, there was 70% of the original organic carbon had lost following deforestation and farming for 15 years. (Zheng et al. , 1996). ØIt is estimated that changes in land use released about 270 Gt CO 2 (Huang et al. , 1998). Deforestation and soil exploitation will increase CO 2 emissions to some extent. 6/13/2021 46

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. 6/13/2021 47

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 4. Use of waste materials in agriculture and their contribution to greenhouse gas emissions Ø It is estimated that about 1/3 of the total N 2 O emissions from agriculture is released by animals. ØThe global CH 4 emissions from the animal waste materials amounts to about 28. 42 Gt (Gou et al. , 2000). ØCH 4 emissions by ruminants account for some 84 % of the total emissions by livestock (Laville et al, 1999). 6/13/2021 48

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 4. Use of waste materials in agriculture and their contribution to greenhouse gas emissions Ø 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 CH 4 and N 2 O emission fluxes. ØBurning 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. 6/13/2021 49

II. GREENHOUSE GAS EMISSIONS IN AGROECOSYSTEMS 4. Use of waste materials in agriculture and their contribution to greenhouse gas emissions Ø It is estimated that some 8. 7 Gt of dry matter is burned on an annual basis around the world. Emission Flux 6/13/2021 CH 4 0. 022 Gt (Xu et al. , 2000) N 2 O 0. 000435 Gt (Laville et al, 1999) 50

III. PRACTICES TO MITIGATE GREENHOUSE GAS EMISSIONS IN AGRICULTURE Two ways to mitigate greenhouse gas : Ø to reduce the existing emission sources Ø to enhance the absorbing capacity of current agricultural sinks as well as creating new ones 6/13/2021 51

III. PRACTICES TO MITIGATE GREENHOUSE GAS EMISSIONS IN AGRICULTURE 1. Mitigating CH 4 emissions A. 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 6/13/2021 52

III. PRACTICES TO MITIGATE GREENHOUSE GAS EMISSIONS IN AGRICULTURE 1. Mitigating CH 4 emissions A. 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 CH 4 • Use of CH 4 inhibitor: application of urease, hydroquinol and dicyandiamide to the soil 6/13/2021 53

III. PRACTICES TO MITIGATE GREENHOUSE GAS EMISSIONS IN AGRICULTURE 1. Mitigating CH 4 emissions B. Animal production Techniques to be applied for reducing CH 4 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. 6/13/2021 54

III. PRACTICES TO MITIGATE GREENHOUSE GAS EMISSIONS IN AGRICULTURE 1. Mitigating CH 4 emissions B. Animal production Techniques to be applied for reducing CH 4 emissions from ruminants • Using growth promoter can reduce CH 4 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. 6/13/2021 55

III. PRACTICES TO MITIGATE GREENHOUSE GAS EMISSIONS IN AGRICULTURE 1. Mitigating CH 4 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 6/13/2021 56

III. PRACTICES TO MITIGATE GREENHOUSE GAS EMISSIONS IN AGRICULTURE 1. Mitigating CH 4 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 6/13/2021 57

III. PRACTICES TO MITIGATE GREENHOUSE GAS EMISSIONS IN AGRICULTURE 1. Mitigating CH 4 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 6/13/2021 58

III. PRACTICES TO MITIGATE GREENHOUSE GAS EMISSIONS IN AGRICULTURE 2. Mitigating N 2 O emissions Because the most significant impact on N 2 O emissions come from irrigation and fertilization, N 2 O emissions can be reduced through soil water control and rational fertilization. 6/13/2021 59

III. PRACTICES TO MITIGATE GREENHOUSE GAS EMISSIONS IN AGRICULTURE 2. Mitigating N 2 O emissions • 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 N 2 O 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 N 2 O emissions. 6/13/2021 60

III. PRACTICES TO MITIGATE GREENHOUSE GAS EMISSIONS IN AGRICULTURE 2. Mitigating N 2 O 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 N 2 O production and emissions. • Use of N 2 O inhibitor The hydroquinol, dicyandiamide, benzoic acid, nitropyrimidine can significantly restrain N 2 O emissions (Tenuta et al. , 2000; Brown et al. , 2000). • Breeding new varieties 6/13/2021 61

III. PRACTICES TO MITIGATE GREENHOUSE GAS EMISSIONS IN AGRICULTURE 3. Mitigating CO 2 emissions The methods for mitigating CO 2 emissions in agroecosystems are divided in two sections. One is addressing the decrease of CO 2 emissions from existing sources, while the other is proposing to reinforce the absorbing ability of CO 2 "sink" as well as creating new CO 2 "sinks". 6/13/2021 62

III. PRACTICES TO MITIGATE GREENHOUSE GAS EMISSIONS IN AGRICULTURE 3. Mitigating CO 2 emissions • Changing land use Reducing the development of waste land; Using the existing farming land more sustainably; returning fallow land to forest, grassland 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. 6/13/2021 63

III. PRACTICES TO MITIGATE GREENHOUSE GAS EMISSIONS IN AGRICULTURE 3. Mitigating CO 2 emissions • Bio-fuel production Ø As the bio-fuel results from the assimilation of atmospheric CO 2, burning of bio-fuel will not increase atmospheric CO 2. It is more favorable to mitigate CO 2 emission than burning mineral fuel. Ø Regions with high production potential should take maximum advantage of fallow land to plant trees and other crops as bio-fuel feedstock. 6/13/2021 64

IV. SOME MEASURES OF GREENHOUSE GAS MITIGATION IN CHINA q Improving the water management techniques Continuous flooding during the rice growing season is changed to midseason drainage, which greatly decreases CH 4 emissions. q 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 CO 2 and 210 thousand tons of CH 4 emission. (Wang, 2003) CO 2 CH 4 6/13/2021 energy-saving kitchen range 84. 46% 73. 05% The marsh gas pool 13. 63% 21. 40% 65

IV. SOME MEASURES OF GREENHOUSE GAS MITIGATION IN CHINA q 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. 6/13/2021 66

V. SUMMARY F CH 4 emissions originate mainly from rice paddy fields, and are impacted by soil characteristics, e. g. temperature, water content, p. H and Eh conditions, and also by land crop management, e. g. land use, rice varieties, fertilizer application. F Rice paddy emits not only CH 4, but also N 2 O. However, the N 2 O emission pattern is quite different from the CH 4 one. Field water conditions and fertilization practices are the main factors that determine N 2 O emissions. 6/13/2021 67

V. SUMMARY F In a farmland ecosystem, CO 2 concentration does not increase, because CO 2 consumption by photosynthesis is greater than CO 2 emission through crop respiration. F The use of waste material in agriculture and breeding development contributes also to greenhouse gas emissions. F 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. 6/13/2021 68

V. SUMMARY F Because the effects of these measures on the different greenhouse gases are different, specific practices must be developed and adopted for the different gases. 6/13/2021 69

Thank You 6/13/2021 70