The relationship between length of fallow and crop yields in shifting cultivation: a rethinking

Rethinking the relationship between length of fallow and crop yields inshifting cultivation?The theory that a correlation between shortened fallow periods and yielddecline in shifting cultivation exists is questioned in this paper. Thisrelationship has been taken for granted, and because it shows that shiftingcultivation will break down under pressure, it has partly been responsible fornegative government views on shifting cultivation. Yield levels in shiftingcultivation are influenced by a wide range of biophysical, socioeconomic, andcultural factors and it is difficult to isolate fallow length as a singledetermining factor. A total of 330 studies were reviewed and fifteen withempirical data were chosen for in-depth analysis. Although most of the empiricalstudies support the theory, the data sets are often ambiguous and importantparameters are insufficiently taken into account. Several studies found norelationship between fallow length and yield, but these also lack information toverify the validity of the data. It is concluded that empirical studiesfocussing on this problem are needed to fully understand this relationship anddevelop feasible scenarios for the numerous attempts at modelling shiftingcultivation development. Moreover, the use of gloomy `breakdown' scenarios asjustification for improving shifting cultivation should be avoided.[PUBLICATION ABSTRACT]