EFFECT OF THE SYSTEM OF RICE INTENSIFICATION (SRI) ON ...

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Figure 2. Effects of applying rice straw outside the season and draining continuous flooded rice fields. Units are in emissions of kg CH4 km -2 a -1 year -1 .Yan et al. (2009). Yagi & Minami (1990) also studied effects of soil types on methane emissions and concluded that soils with high OM content have a higher influence on CH4 than soils with low OM content. Thus emitting more methane than soils low in OM is most likely due to a lower anaerobic decomposition. Resource poor farmers (RPF) who cannot afford to invest in mineral fertilizers rely on natural amendments such as compost and green manure. The most sustainable amendments would seem to be composts as compost only slightly increase methane emissions compared to green manure and rice straw (Neue, 1993; Yagi & Minami, 1990). Compost combined with mineral fertilizers decreased CH4 emissions from rice fields in India twice as much as mineral fertilizers alone (Nayak et al., 2007) indicating that possible combinations of these two amendments would be ideal. 3.3 Management practices and their effect on GHG emissions Management practices such as puddling will have some effect on GHG emissions. Harada et al., (2007) studied the effect of no puddling in irrigated rice farming and found that the emissions of CH4 was 43% lower than in conventional puddling practices in Japan. CO2 emissions from no puddled fields were 1740 kg CO2 ha -1 lower than in puddled fields (Harada et al., 2007). It is though questionable if RPF conduct puddling. De Datta (1987) states that large quantities of water 20
are required (app. 150-200 mm) and farmers producing lowland rainfed rice are forced to wait app. one to three months before there is enough water to puddle. 3.4 Drainage periods and GHG emissions The effects of a changing water level in a rice field leading to anaerobic and aerobic conditions will influence GHGs emissions and especially methane emissions. Wassmann et al., (2000) conducted studies on CH4 emissions from five locations in Asia and discovered that soils amended with organic manure had higher emissions of GHGs compared to soils fertilized with mineral fertilizers. Intermittent flooding and mid season drainage resulted in lower emissions than with conditions of continuous flooding (Wassmann et al., 2000). Emission rates ranged from less than 100 kg CH4 ha -1 to more than 400 kg CH4 ha -1 for intermittent irrigation and continuous flooding respectively (Wassmann et al., 2000). Emissions were different within the different periods of the rice crop with highest emissions during the reproductive stage and the highest temperatures (Wassmann et al., 2000) which is also true for the other GHGs. Drainage periods will lower CH4 but will however affect the emission rates of N2O. Yue et al. (2005) compared continuous flooding with intermittent flooding and their role on CH4 and N2O emissions in Southern China and found that intermittent flooding showed a 17% lower GWP compared to continuous flooding while there was no significant differences between yields. Methane emissions decreased but N2O increased with intermittent flooding but the trade-off was the most optimum as compared to continuous flooding (Yue et al., 2005). Zou et al. (2005) found that in Chinese rice fields with continuous flooding N2O emission rates was 0.03 mg m -2 d -1 as compared to rice cropping with a mid season drainage of 14.1 mg m -2 d -1 . Both treatments received 2.25 t ha -1 of wheat straw. Mid season drainage periods are often used in China and Japan but not to a large extent in warmer rice growing climates (Greenland, 1997). The effect of drainage in the Cambodian climate, which is very different from the Chinese and Japanese climatic situation, might result in different emission rates due to temperature and a faster decomposition of OM. Water management involving mitigation interests or because of water shortages will have large influences on emission rates of CH4, N2O and CO2 with many trade-offs involved (Frolking et al., 2004). A farming system trying to involve mitigation of all three GHGs and involve and deal with the trade-offs would be an optimal one. But which system can cope with such challenges and still sustain the farmer and his family? 21
Page 1 and 2: EFFECT OF THE SYSTEM OF RICE INTENS
Page 3 and 4: Abstract The System of Rice Intensi
Page 5 and 6: Preface This report is part of my M
Page 7 and 8: Table of contents Preface..........
Page 9 and 10: 1. Introduction Rice (Oryza sativa
Page 11 and 12: fields will normally result in lowe
Page 13 and 14: materials. These two chapters lead
Page 15 and 16: the process of puddling - which is
Page 17 and 18: Crop residues The use of rice straw
Page 19: The degree of GHGs emissions will t
Page 23 and 24: • The use of young seedlings tran
Page 25 and 26: Table 1. The major differences betw
Page 27 and 28: Cambodia during modern times. In 19
Page 29 and 30: Rainfed rice in Cambodia is often g
Page 31 and 32: In general there are three types of
Page 33 and 34: 7. Study and experimental implement
Page 35 and 36: growing rice but the Cambodian rain
Page 37 and 38: Figure 6. Map of the two target com
Page 39 and 40: The following main topics were exam
Page 41 and 42: White & Seng (1997) state that not
Page 43 and 44: conditions signifying little or no
Page 45 and 46: Riel 3000000 2800000 2600000 240000
Page 47 and 48: The involved farmers seem to belong
Page 49 and 50: The farmers’ composts were often
Page 51 and 52: chemical fertilizers. It is part of
Page 53 and 54: 9.5.2 SRI techniques The different
Page 55 and 56: t/ha 5,5 5 4,5 4 3,5 3 2,5 2 1,5 1
Page 57 and 58: the farmers are with SRI. Or farmer
Page 59 and 60: forced to sell labour in order to s
Page 61 and 62: households were in average able to
Page 63 and 64: K, only a minor fraction is availab
Page 65 and 66: Table 8. An estimated picture of an
Page 67 and 68: fertilizers which can increase N2O
Page 69 and 70: Table 9. An estimated C budget. It
Page 71 and 72:
10. Conclusion The farmers particip
Page 73 and 74:
11. References Anthofer, J. 2004. T
Page 75 and 76:
Moldenhauer, K.A.K. & Gibbons, J. 2
Page 77 and 78:
Yue, J., Shi, Y., Liang, W., Wu, J.
Page 79 and 80:
APPENDIX B. Soil sampling methodolo
Page 81 and 82:
Type How much do you apply to your
Page 83 and 84:
APPENDIX E. LIVELIHOOD ASSESTS. Per
Page 85 and 86:
3 2 1 Combination of SRI techniques
Page 87:
APPENDIX F. Interview with Ma Veasn
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