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

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doubtful if such measure would work for the RPF as they would have to increase input costs on pesticides which they do not have. To really affect and increase the C pool, the inputs of biomass must be larger than the losses of C (Lal, 2007) and thus taking the steady state to a new level. Given the amount of trees planted in the ILFARM project (500.000) this would mean 625 trees per participating household (800 in total). The available input of biomass would then app. at least be the double resulting in 6 t ha -1 (incl. compost). Such a double input would result in a net balance of 116 kg C ha -1 in excess after mineralization per year. For long term effects (20-30 years), assuming farmers would apply at least 6 t ha -1 , this would result in a C pool of 51.5 t C ha -1 and 53 t C ha -1 respectively which is a rather small increase. However farmers will reach a sustainable rice production with high yields (3.5 t ha -1 ) and a slowly increasing C pool improving soil quality in the long run. However producing and transporting such large quantities of biomass is very labor intensive and only larger families (richer) will be more likely to cope with such a scenario. It is however unlikely that both small and larger households will convert all their land to SRI, as it requires intensive labor. A more likely scenario is that farmers will use some of the SRI techniques and mix them into their traditional system. Farmers conducting SRI will sometimes stop after a few years and then start mixing their traditional systems with SRI (Ma Veasna, personal communication, 2008). 68
Table 9. An estimated C budget. It is assumed that farmers convert all their land to SRI and have an annual compost production of 3t/ha and a rice yield of 3.5 t/ha. Inputs kg C ha Specifications References Roots 210 Undecomposed 42% C estimated from Brady & Weil, (1999a).Root shoot ratio estimated from Yoshida (1981) to be 0.1 Stubble 110 Undecomposed 42% C estimated from Brady & Weil, (1999a). Stubble estimated to be 5% of the straw mass (5.25 t/ha) Compost 1050 Undecomposed C% of the compost is estimated to be 35% Total 1370 Losses Roots 141 67% lost Estimated from Brady & Weil (1999a) Stubble 94 85% lost Estimated from Brady & Weil (1999a) Compost 788 75% lost Estimated from Brady & Weil (1999a) Total 1022 Net balance 348 Soil C pool = 49.5 t/ha A perfect SRI system as described by e.g. Stoop et al., (2002) compared to conventional rice systems will most likely emit less amounts of GHGs and increase C pools due the water management involving several drainage periods. The SRI practiced by the targeted farmers within this project does not seem to possess the means of really affecting a decrease of GHG emissions due to no water management. The potentials of increasing the C pool does however seem more appropriate for the RPF in Prey Veng with the input of 500.000 trees over the next years. On the basis of the discussion on GHG emissions and C sequestration, it is tempting to state that SRI is moving the target farmers’ livelihood sustainability towards a new and higher level. Or as stated by Pretty (2000) on the definition of a sustainable farming system being one that: “..sequesters carbon in soils through organic matter accumulation both contributes to the global good by mediating climate change and the private good by enhancing soil health”. RPF can turn a rice based farming system emitting large amounts of GHGs into a sustainable one (such as SRI or other systems) through C storage and develop a beneficial system with long term effects on increased soil quality and productivity. By reducing the emissions of GHGs, soil C is increasing in combination with applied organic materials and soil fertility can increase hence have a large positive influence on their livelihood strategies and future life. 69
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EFFECT OF THE SYSTEM OF RICE INTENS
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Abstract The System of Rice Intensi
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Preface This report is part of my M
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Table of contents Preface..........
Page 9 and 10:
1. Introduction Rice (Oryza sativa
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fields will normally result in lowe
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materials. These two chapters lead
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the process of puddling - which is
Page 17 and 18: Crop residues The use of rice straw
Page 19 and 20: The degree of GHGs emissions will t
Page 21 and 22: are required (app. 150-200 mm) and
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: fertilizers which can increase N2O
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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