Exploring diversity within smallholder farming systems in Zimbabwe : nutrient use efficiencies and resource management strategies for crop production.

This thesis characterizes the dynamic and spatial variability of soil fertility on smallholder farms in Zimbabwe and its effects on crop production. Appropriateness of resource management strategies for the heterogeneous biophysical and socio-economic conditions on the smallholder farms is also explored.

Assessment of soil organic C (SOC) contents along cultivation chronosequences revealed rapid decline in SOC within the initial 5 years of cultivation when woodland soils were cleared for subsistence maize cultivation without fertilizer inputs. Commercial farming with intensive use of mineral fertilizers and incorporation of maize stover led to more gradual decline of SOC: at equilibrium, contents of SOC in a clay soil were 15 t C ha-1 greater than the contents in a similar soils on smallholder farms...