A longterm field experiment on organic material application and crop rotation with green manure crops
has been conducted since 1976 at Lopburi Agricultural Research and Development Center,Department of Agri鄄
culture,Lop Buri Province,Thailand,to clarify the effect of organic materials and green manure crop on soil or鄄
ganic carbon changes. The stock change factors that stand for the relative change of soil organic carbon on the
carbon stock in a reference condition ( native vegetation that is not degraded or improved). Stock change factor
for input of organic matter (FI
) ,representing different levels of C input to soil such as organic material appli鄄
cation,crop residue treatment and green manure crop cultivation,was computed with the present field experi鄄
mental results. While the computed FI
of “High input with manure冶 was within the range of IPCC default FI
value,some of the computed FI
of “High input without manure冶 was much higher than the IPCC default though
it was varied due to the biomass production and nutrient contents of the green manure crops planted as the sec鄄
ond crops after corn. Therefore,the FI
computed by field experimental results can contribute to more accurate
estimation of SOC changes in farm land especially in Southeast Asia because the default FI mostly depends on
the experimental data in temperate zones. Moreover,the field experiment has focused the effect of reduced till鄄
age practices on SOC changes and corn yield since 2011. The results of the experiment will be used to compute
Stock change factor for management regime (FMG ) which represents the effects of tillage operations郾