What methodology will be most suitable and relible for studying the "PARTICIPATORY DEVELOPMENT: A TOOL FOR ALLEVIATION OF RURAL POVERTY AND PREVENTION OF ENVIRONMENTAL DEGRADATION FOR SUSTAINABLE DEVELOPMENT
As an aside, I think it is worth noting that "participatory development" schemes in some countries (I am most familiar with the cases of Nigeria and Ghana) can end up being a sort of Orwellian appropriation of language where the "participatory" aspect is simply that the government has mobilized some or all of the population into supporting and working for some particular plan in an area.
However, I would always consider "participatory development" as a PROCESS which goes to great lengths to involve local populations in decision making processes, most likely through representative participation of all relevant groups in providing inputs, in the form of expressing their specific local knowledge and the interests of that group, so that decision makers can incorporate new information and balance different interests.