In recent years the accepted organizational pattern of relations between science and production has begun increasingly to be called in question. In the area of peasant agriculture, this generally takes the form of a critique of a system based upon centralized research institutes and hierarchically administered extension agencies. This paper explores this theme by means of an empirical study of the impact of rhizobium inoculant technology on selected areas of peasant agriculture in Thailand. The paper shows that this (core) scientifically derived technology has had widely different effects in different locations, and that these involve complex interactions with different biological systems. The evidence suggests that there are independent knowledge systems possessed by farmers who combine this knowledge innovatively with the core technology to produce outcomes that vary over time and space. The case, in common with many others, indicates also that core scientists are reluctant to accept technological complexity, preferring instead to leave responsibility for application to the extension system, even when it is clear that more research may be necessary.