Avant-Propos

Demographic pressure in African countries requires that the production of cash crops and food crops be simultaneously increased. Both are necessary for food security. This work identifies the conditions under which such a challenge can be carried out. By using results of field surveys and models of cocoa and coffee farming systems, it demonstrates that complementarities between crops are based on the exploitation of the "agro-ecological" capital. It also shows to what extent liquidity constraints may limit input intensification. It finally explains how conditions under which food crops are produced determine the shadow price of labour. It assesses to what extent this price is a key factor in the competitiveness of cash crops.