Despite improvements in many other regions, sub-Saharan Africa has continued to experience a decline in food security and agricultural productivity per capita, leading to an increase in undernourishment since 1990 (Food and Agricultural Organization [FAO], 2006; Toenniessen et al., 2008). Biophysical challenges to food security include productionlimiting constraints faced by resource-poor farmers, such as shrinking farm sizes and inequitable land distribution patterns, depleted soils and limited use of fertilizer and soil amendments, unreliable rainfall and lack of irrigation capacity, inadequate pest and disease control, and limited access to improved varieties and seed distribution systems (Diao et al., 2007).