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

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the Madagascan government stopped the subsidies for chemical fertilizers and farmers had to seek new alternatives and the use of compost hence became more important (Satyanarayana et al., 2007). It should be notified that SRI should not be regarded as a fixed system, but one that will differ between countries and regions because it depends on the agro-ecological characteristics in a given area (Stoop & Kassam, 2005). The reason why less water is stressed to be so important is due to several reasons. Normally rice is categorised as being an aquatic plant due to its formation of aerenchyma cells in the roots under flooded conditions – but is not necessarily because rice will grow better under such conditions (Kabir, 2006) as there is no evidence that flooded conditions will result in better plant growth (Stoop et al., 2002). Dobermann (2004) however states that the reason why the rice plant developed the aerenchyma cells is due to its evolution from being native to wetlands because conditions were more favourable there with more nutrients and less competition. Continuous flooding is though believed to decrease root growth due to lack of oxygen (Satyanarayana et al., 2007). The idea of keeping soils just moist and not flooded will enhance a larger root growth making the rice plants more adapted to situations with water stress (Kabit & Uphoff, 2007) which are typical for rainfed lowland systems (Greenland, 1997; Javier, 1997) creating shortage of water for the plants (Seng et al., 1999). Lowland rainfed systems are discussed more in section 5.2 and 7.1. The use of younger seedlings is believed to result in an improved and larger root growth (Satyanarayana, 2004) which will take up more nutrients (Kabir, 2006) and hence improve growth and yield potential of the rice plant. 4.3 The differences between SRI and a traditional/conventional rice system There are large differences between SRI and traditional/conventional rice production methods. Table 1 below illustrates these variations where especially the amount of seeds needed per ha and age of seedlings are some of the major differences. 24
Table 1. The major differences between SRI and conventional rice production methods. Taken from Stoop et al. (2002). There are however large disputes concerning SRI and its successes with farmers as there are many pros and cons. Supporters claim that SRI often yield the double of conventional rice farming, but opponents state that there is no scientific evidence for such potentials (Surridge, 2004). There are however many experiments which illustrate the benefits of SRI and those that illustrates that there is no difference between SRI and conventional rice growing. Very high yields have been reported with SRI as compared to traditional farming or farmers practice. Table 2 below illustrates some of the reported high yielding situations from rice growing countries. Table 2. SRI vs. farmer practice yields. SRI (t/ha) Conventional - Farmer Practice (t/ha) Specifications Country Reference 7,4 2,5 N = 10 Gambia Caesay (2002) 5,3 2,5 N = 8 groups of 20 farmers. Sierre Leone Yamah (2002) 7-15 Madagascar Stoop et al., (2002) 6,5 2,08 Myanmar Kabir & Uphoff (2007) 2.3 1,6 N = 500 Cambodia Anthofer (2004) Such yields as described above are though according Dobermann (2004) not scientifically reliable and non comparable to conventional rice growing. Dobermann (2004) further states that in many experiments where SRI is compared to conventional farming a scientific methodology has not been followed and it is therefore very difficult to compare the two systems. McDonald et al., (2006) compared and compiled data from yields between SRI and conventional rice growing in China, Laos, Nepal, Thailand, India, Sri Lanka, Indonesia, Bangladesh, and the Philippines and found that in a majority of these countries SRI provided lower yields than conventional growing. Sheehy et al. (2004) compared SRI with conventional grown rice at three sites in China regarding grain yield, number of panicles, spikelets per panicle, grain filling and grain weight and found no difference between the two methods. Sheehy et al. (2004) further states that the very high reported yields from Madagascar are not possible and are due to measurement errors. 25
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 and 20: The degree of GHGs emissions will t
Page 21 and 22: are required (app. 150-200 mm) and
Page 23: • The use of young seedlings tran
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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