Agroforestry for soil-fertility replenishment: evidence on adoption processes in Kenya and Zambia

摘要

Sub-Saharan Africa (SSA) is the only region in the world where the number of poor people has been increasing in the past decades. The World Bank (2000a) estimated the number of poor (less than US1 dollar day~(-1) of income) to have risen from 242 million in 1990 to 291 million in 1998, nearly half of the population. Unlike other regions of the world, most of the poor in SSA continue to reside in rural areas, owing to poor growth in industrial and service-sector jobs. A key component of the rural poverty complex is the declining per capita food-production trend over the past 30 years (Badiane and Delgado, 1995; World Bank, 1999). While opportunities for agricultural land expansion are worsening, yield increases in relation to the rest of the worldhave been dismal. One of the reasons for poor yield performance is the woefully low use of mineral fertilizers (FAO, 1996; Larson and Frisvold, 1996; Gladwin et al, 1997a; Mwangi, 1997). Another reason is the estimated high rate of soil erosion due to insufficient conservation measures and consequent loss of fertility (Bojo, 1994; Bishop, 1995). Together with poor cycling of nutrients, negative farm nutrient balances have been found to be common (Stoorvogel and Smaling, 1990; Soule and Shepherd, 2000).