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

high compared to other doses (see table 6). 1.9 kg m -2 corresponds to 19 t/ha which is a very large
amount for small scale farmers to produce/collect and very labour intensive. Almost 50% of the
farmers do however apply both compost and green manure and such a method will lead to many
possibilities on finding the necessary means and amounts of amendments needed in order to reach a
sustainable level of inputs.
The amount of compost collected per year will cover the increase next year, but the amount of
natural fertilizers collected will not be enough. Farmers only relying on natural fertilizers will need
to find additional amounts of organic amendments. In theory the more compost the farmers apply
the higher the yield and improved soil quality they will reach. Uphoff (1999) reports from SRI
practising farmers in Madagascar that amount and quality of added composts was very different
from farmer to farmer and those with highest yields did also apply high amounts of compost or had
a higher soil quality than other farmers. Husain et al. (2004), Mcdonald et al. (2006) and
Satyanarayana et al. (2007) state that a major limitation for farmers practising SRI is the lack or low
quantity of organic amendments applied to fields, which will decrease benefits of SRI. SRI can
however very well be practiced with chemical fertilizers (Laulanie, 1993) but only few farmers can
afford to buy these or have been encouraged by CEDAC not to use them and instead focus more on
natural amendments. The farmers will through the ILFARM project receive app. 500.000
multipurpose trees to plant on their homestead land and around rice fields in order to increase
production of especially green manures (leaf manures). See Appendix E. Depending on which rate
and amount of added compost/fertilizers farmers will somehow be forced to grow a certain area of
SRI. They can choose to apply less amounts per m 2 thus reaching a larger area but with the given
soil conditions (low C and N) the need for large applications is necessary in order to reach
sustainable yields.
9.5.5 Nutrient balance
Assuming the farmers convert all their rice land to SRI and obtain average rice yields of 3.5 t/ha,
and the increase in leafy manures together with increased compost production will reach an average
amount of 3t/ha per year. A rough estimate of a nutrient budget could then look like the illustration
in Table 8. The net balance indicate that N and P inputs are in excess but the K pool is being
depleted most likely due to the removal of straw, which is typical for rice systems with removal of
residues (Greenland, 1997; Dobermann & Fairhurst, 2000). However given the inputs of N, P and
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