Many studies have stressed the importance of trees to rural households. Few, however, have focused on actual numbers and densities of trees in different land-use systems. Based on community-level participatory research in six communities, semi-structured household interviews and full-farm fruit tree inventories, this study aims to understand farmers' tree-planting strategies. Relationships between the diversity, number and density of fruit trees and farm size, land-use system, land tenure, distance from the homestead, proximity to the forest, market access and household characteristics are investigated. The key factors determining the differences in tree-growing strategies between communities appear to be market access, land use and access to forest resources. Within communities, differences between individual households were less easy to explain but tenure was important as was farm size. Smaller farms had higher fruit tree densities, a relationship that was particularly strong in communities with good market access. Overall there was a great deal of variability both within and between communities and many of the factors affecting tree-planting decisions were found to be highly inter-related. Despite this complexity, trees on farm play an important role in rural household's livelihoods. Therefore, expansion of tree cultivation should be recognized as a promising pathway to achieve increased income and food production by policy makers and extensionists alike. In addition to improved tree propagation and management techniques, farmers should be strengthened in the processing and marketing of agroforestry tree products and more emphasis should be placed on the development of tree enterprises. By doing so, farmers will be able to earn a more important and consistent income from fruit trees, contributing to the Millennium Development Goals.

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The flows and balances of N, P and K were studied in 20 farms in the Campo Ma'an area in Cameroon between March and August 2002 to assess the nutrient dynamics in smallholder farms. Data were collected through farmer interviews, field measurements and estimates from transfer functions. Nutrient input from mineral (IN1), animal feed (IN2a) and inorganic amendments (IN2b) was absent. Major outputs were through crop (OUT1a) and animal (OUT1b) products sold. Partial budgets for farmer managed flows were negative: À65 kg N, À5.5 kg P and À30.8 kg K ha À1 year À1 . For inflows not managed by farmers, deep capture (IN6) was the major source: 16.6, 1.4 and 6.6 kg ha À1 year À1 of N, P and K, respectively. Atmospheric deposition (IN3) was estimated at 4.3 kg N, 1.0 kg P and 3.9 kg K ha À1 year À1 , and biological nitrogen fixation (IN4) at 6.9 kg N ha À1 year À1 . Major losses were leaching (OUT 3a): 26.4 kg N, and 0.88 kg K ha À1 year À1 . Gaseous losses from the soil (OUT 4a) were estimated at 6.34 kg N, and human faeces (OUT 6) were estimated at 4 kg N, 0.64 kg P and 4.8 kg K ha À1 year À1 . The highest losses were from burning (OUT 4c), i.e. 47.8 kg N, 1.8 kg P and 14.3 kg K ha À1 year À1 . Partial budgets of environmentally controlled flows were negative only for N À4.8 kg N, +2.4 kg P and +9.6 kg K ha À1 year À1 . The overall farm budgets were negative, with annual losses of 69 kg N, 3 kg P and 21 kg K ha À1 . Only cocoa had a positive nutrient balance: +9.3 kg N, +1.4 kg P and +7.6 kg K ha À1 year À1 . Nutrients reaching the household waste (1.9 kg N, 2.8 kg P and 18.8 kg K ha À1 year À1 ), animal manure (4.9 kg N, 0.4 kg P and 1.6 kg K), and human faeces (4 kg N, 0.64 kg P and 4.8 kg K ha À1 year À1 ) were not recycled. Five alternative management scenarios were envisaged to improve the nutrient balances. Recycling animal manure, household waste and human faeces will bring the balance at À62.6 kg N, 0 kg P and +1 kg K ha À1 year À1 . If, additionally, burning could be avoided, positive nutrient balances could be expected.

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This chapter discusses the progress in participatory tree domestication in West and Central Africa. The steps in participatory tree domestication are discussed: selection of priority species based on farmers' preferences and market; orientation; collection of germplasm from elite trees chosen by farmers or other users; establishment of passport data for trees from which germplasm was collected (for future use in tracing the owners of trees in respect of property right); development of appropriate vegetative propagation techniques for the different species under domestication; integration of improved propagules in different cropping systems; and marketing studies of products from domesticated species.