In the past few decades, chemical fertilizers have widely spread throughout the world focusing that the soil is inert
medium for plant roots, rather than as a living biosphere in which the crop is only one of hundreds or thousands of
interacting species. However, it is now realized that in fields under intensive monoculture which receive heavy
applications of chemical fertilizers alone, there is a slow decline in productivity. This decline occurs even in
irrigated paddy fields (FFTC, 1998).