ABSTRACT

Shifting cultivation amongst the Kammu in Laos has traditionally followed an 11-year cycle. The land had to be left fallow sufficiently long for the trees to form a canopy and smother out unwanted grasses. High trees overshadow the grass and prevent it from getting any sunshine, so it dies. If grass underlying trees does not get enough rain, it also dies. Swidden fields heavily invaded by ferns and elephant grass need to be left idle for two or three cycles before being reopened. If such places are left fallow for 15 to 20 years, the grass disappears and rice grows well again.