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

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).
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