Diversification is in the Detail: Accounting for Crop System Heterogeneity to Inform Diversification Policies in Malawi and Zambia

Crop diversification is a common agricultural policy objective. However, the determinants and impacts of crop diversification are heterogeneous and depend on a range of crop-specific characteristics. Index-based measurements of crop diversification, common in the agriculture economics literature, are unable to account for this heterogeneity. Using two national panel surveys from Malawi and Zambia, we develop a multinomial treatment effects model to examine the determinants of adopting seven discreet cropping systems and their impacts on maize productivity and crop income stability. The results of this approach are compared to those obtained when using a Gini–Simpsons index. Differences between the two empirical approaches highlight the importance of accounting for cropping system heterogeneity when conducting analyses of crop diversification to inform policy. For example, in Zambia, we show that levels of output market competition have no significant effect on diversification when diversification is measured as an index. However, at a cropping system level increased private trader activity is associated with a reduced probability of adopting subsistence-oriented cropping systems and an increased probability of adopting more productive and commercialised systems.