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Managing agricultural soils to mitigate CH 4 emission from rice-based cropping systems in China Zucong Cai Institute of Soil Science Chinese Academy of.

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Presentation on theme: "Managing agricultural soils to mitigate CH 4 emission from rice-based cropping systems in China Zucong Cai Institute of Soil Science Chinese Academy of."— Presentation transcript:

1 Managing agricultural soils to mitigate CH 4 emission from rice-based cropping systems in China Zucong Cai Institute of Soil Science Chinese Academy of Science

2 Mitigation of CH 4 emissions from permanently flooded rice fields is a priority Option 1

3 Crop rotation and management of rice-based agro-ecosystems Rice season Non-rice season Apr-Jun Sep-Nov Non-rice season Drained and cropped Winter wheat, oil-seed rape…… Drained and green manure Fallow under drained conditions under flooded conditions Rice season Double rice crops (Apr-Oct or Nov) Single rice crop (Jun-Oct or Nov) Middle rice crop (May-Aug or Sep

4 Rice fields under fallow and flooded conditions in winter Total area: Mha Distribution: Mainly in mountainous and hilly area in Southwest China Poor drainage conditions

5 A kind of rice fields with the largest CH 4 emission

6 How to mitigate CH 4 emission from permanently flooded rice field?

7 The experiment was setup in 1990 Research on CH 4 emission was conducted in four treatments of the experiment from 1995 to 2000 Experimental farm of China Southwest Agricultural University, Chongqing

8 Design of field experiment in Chongqing Rice seasonNon-rice season Ch-FF Ch-FFR Rice seasonWinter upland crop Ch-Wheat Ch-RW Winter upland crop

9 Temporal variation of CH 4 flux during rice growing period Ch-FFCh-FFR Ch-WheatCh-RW

10 Mean CH 4 flux during rice growing period (mg CH 4 /m 2 /h) b 16.5a 10.0a 18.5ab 31.3b 12.4a Average Mean ND Ch-RWCh-WheatCh-FFRCh-FFYear

11 Temporal variation of CH 4 flux during winter season Ch-FF Ch-FFR

12 Correlation coefficient (r value) between CH 4 flux and soil temperature in winter season **0.6281**1999/ **0.6340**1998/ / **0.6296**1995/96 Ch-FFRCh-FFYear

13 Mean CH 4 flux (mg CH 4 /m 2 /h) during the winter season 5.0b8.4aAverage / / / /96 Ch-FFRCh-FFYear

14 Annual CH 4 emissions from various treatments of a permanently flooded rice field 100% 67% 33% 36%

15 There was no significant difference in rice crop yield among the treatment

16 Mitigation potential if permanently flooded rice fields were completely drained in non-rice growing season According to the second soil survey of China, there are 2.52 Mha of gleyic paddy soils, which are permanently flooded. Using month-mean temperature and the relationship between temperature and CH 4 flux to estimate CH 4 emissions from gleyic paddy soils by province CH 4 emission from gleyic paddy soils in China is estimated to be 0.78 Tg CH 4 during the non-rice growing season

17 Managing paddy soil as dry as possible in winter season is able to mitigate CH 4 emission from rice fields Option 2

18 Relationship between soil moisture in the non-rice growing season and CH 4 emission during the following rice growing period (greenhouse experiment)

19 Moisture of surface soil in the non-rice growing season was controlled by ground water table in a lysimeter 60 cm 40 cm 20 cm Flooded

20 Relationship between soil moisture in the non-rice growing season and CH 4 emission during the following rice growing period (lysimeter experiment) Ground water, cm 98/99 soil moisture g/g Mean CH 4 flux mg CH 4 /m 2 /h 99/00 soil moisture g/g Mean CH 4 flux mg CH 4 /m 2 /h Flooding

21 Relationship between soil moisture in the non-rice growing season and CH 4 emission during the following rice growing period (field measurement in Chongqing)

22 Field flux measurement sites in China Fengqiu Nanjing Jurong Suzhou Yingtan Changsha Guangzhou Chongqing

23 CH 4 emissions measured across China could be described by the soil moisture in the non-rice growing season

24 At the national scale, precipitation would be a dominant factor controlling regional variation of soil moisture in the non-rice growing period. But to a certain rice field, soil moisture in the non-rice growing period is dependent up topography and management. Managing rice fields well-drained, avoiding waterlogged, and making soil moisture as low as possible in the non-rice growing season would mitigate CH 4 emission during the following rice growing period.

25 Rotating flooded rice with upland crop(s) would also mitigate CH 4 emissions from rice fields during rice growing period Option 3

26 Effect of wet rice and upland crop rotation (Guangzhou) Rice season 27% 8% Upland crop100% Relative CH 4 emission

27 Application of organic manure at the start of upland crop season instead of before rice transplanting significantly decreases CH 4 emission during the rice growing period Compost before application of organic manure would also reduce the stimulation effect of organic manure on CH 4 emission Option 4

28 Effect of rice straw application time on CH 4 emission in wet rice and upland crop rotation system (Greenhouse experiment) Upland seasonRice season Upland season Rice season Straw application Mean CH 4 flux: 4.52 Mean CH 4 flux: 3.52 Mean CH 4 flux: 18.3 Mean CH 4 flux: 28.6

29 Option 4 Intermittent irrigation (multiple mid- aeration) during rice growing period Chemical fertilization Others

30 Comparisons of CH 4 emissions between intermittent flooding (IF) and continuous flooding (CF) during rice growing period averaged over available data in China Rice season Mean CH 4 flux, mg CH 4 /m 2 /h IFCFIF/CF, % Early rice Middle rice Late rice

31 Effect of nitrogen fertilizers on CH 4 emission during rice growing period Rate kg N/ha Mean CH 4 flux mg CH 4 /m 2 /h Mean N 2 O flux g N/m 2 /h Urea(NH 4 ) 2 SO 4 Urea(NH 4 ) 2 SO

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