General
Smallholder livelihoods in sub-Saharan Africa(SSA) are constrained by a number of factors that limit food production and thereby threaten food security. Soil fertility is one of the major factors explaining the decrease in per capita food production in SSA. Nutrient deficiencies in particular N and P severely limit agricultural production in many regions in the tropics. Supply of adequate amounts of nutrients throughfertiliserapplication is therefore a prerequisite to balance soil fertility budgets and to boost food production. However, mineral fertilisers are not accessible to the large majority of smallholder farmers. Farmyard manure, an important source of organic fertiliser for smallholder farmers, is available at limited quantities due to low livestock densities in many regions, for example Rwanda. Agroforestry, a low-input technology, was shown to contribute to the enhancement of food production while ensuring sustainability in sub-Saharan Africa.Agroforestry may contribute to soil fertility by increasing nutrient availability and providing other various benefits and services. However, to be successful agroforestry technologies need to match the characteristics of different smallholder farming systems, like for example soil fertility status, socioeconomic status and farmer management. These factors are rarely studied in an integrated manner.
This thesis aims to understand and characterise different farming systems, ...