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This paper follows the transition from ethnobotany to a deeper scientific understanding of the food and medicinal properties of African agroforestry tree products as inputs into the start of domestication activities. It progresses on to the integration of these indigenous trees as new crops within diversified farming systems for multiple social, economic and environmental benefits. From its advent in the 1990s, the domestication of indigenous food and non-food tree species has become a global programme with a strong African focus. This review of progress in the third decade is restricted to progress in Africa, where multi-disciplinary research on over 59 species has been reported in 759 research papers in 318 science publications by scientists from over 833 research teams in 70 countries around the world (532 in Africa). The review spans 23 research topics presenting the recent research literature for tree species of high priority across the continent, as well as that in each of the four main ecological regions: the humid zone of West and Central Africa; the Sahel and North Africa; the East African highlands and drylands; and the woody savannas of Southern Africa. The main areas of growth have been the nutritional/medicinal value of non-timber forest products; the evaluation of the state of natural resources and their importance to local people; and the characterization of useful traits. However, the testing of putative cultivars; the implementation of participatory principles; the protection of traditional knowledge and intellectual property rights; and the selection of elite trees and ideotypes remain under-researched. To the probable detriment of the upscaling and impact in tropical agriculture, there has been, at the international level, a move away from decentralized, community-based tree domestication towards a laboratory-based, centralized approach. However, the rapid uptake of research by university departments and national agricultural research centres in Africa indicates a recognition of the importance of the indigenous crops for both the livelihoods of rural communities and the revitalization and enhanced outputs from agriculture in Africa, especially in West Africa. Thus, on a continental scale, there has been an uptake of research with policy relevance for the integration of indigenous trees in agroecosystems and their importance for the attainment of the UN Sustainable Development Goals. To progress this in the fourth decade, there will need to be a dedicated Centre in Africa to test and develop cultivars of indigenous crops. Finally, this review underpins a holistic approach to mitigating climate change, as well as other big global issues such as hunger, poverty and loss of wildlife habitat by reaping the benefits, or ‘profits’, from investment in the five forms of Capital, described as ‘land maxing’. However, policy and decision makers are not yet recognizing the potential for holistic and transformational adoption of these new indigenous food crop opportunities for African agriculture. Is ‘political will’ the missing sixth capital for sustainable development?

Soils are the universal reservoirs through which living organisms get the resources for their livelihoods either directly like plants and indirectly like other organisms and animals. The ability of soils to serve as a universal reservoir depends on its fertility. Agroforestry practices have been seen to improve and conserve soil fertility. This research work carried out from the 10th of May 2015 to the 10th of November 2015 was aimed at assessing the role of agroforestry practices in the improvement of soil fertility in the study area. Information was collected using questionnaires, field surveys and the analysis of soil samples in the laboratory. The results obtained were subjected to regression and correlation analysis using the Statistical Package for Social Sciences (SPSS). These results showed that the main agroforestry practices in this area include live fences and scattered trees on farmlands. It was also observed that farmers use indicators such as yields, softening of soil, wilting of the crops, rotten tubers, erosion and rains to determine soil fertility. There was no significant difference between various soil parameters (pH, acidity, CEC, ECEC, C/N, and exchangeable Al) in the two major agroforestry practices identified. There was equally no significant difference between the various soil elements and yields in the two major systems identified. The only element that showed a significant difference (P<5%) in the two systems and also for yields was phosphorous. Since only phosphorous significantly influenced yields in this area, a model was established to show that crop yields are dependent on phosphorous as indicated by the equation Yields = 1.77+ 0.03 P. Scattered trees on farm lands were recommended to farmers, the practice of improved fallow using a local fertilizing species identified as well as the use of Guatemala grass (Tripsacum laxum) and Vetiver grass (Vetiveria zizanoides) should be introduced on slopes to control erosion.

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Faced with the adverse effects of climate variability and change (CVC), agro-ecological farming practices like agroforestry are crucial especially for smallholder farmers who are extremely vulnerable. It was within this context that this study appraised smallholder farmers' agroforestry practices faced with climate change adversities. Biophysical and socioeconomic data were collected from ten villages in Cameroon. Findings showed that climate parameters have experienced significant fluctuations in the past five decades. Smallholder farmers practice several agroforestry practices and integrate a plethora of tree/shrub species on agroforestry plots in order to adapt to climate change. Six main types of agroforestry trees/ shrub species (trees/shrubs used for fuelwood, fruits, building materials, fodder, soil improvement, medicines) were integrated by smallholder farmers within agroforestry plots. T test and Chi-square test statistics indicated a strong noncausal relationship between explanatory variables (institutional and socio-economic attributes) and smallholder farmers' agroforestry practicing decision faced with CVC. Logistic regression showed that a strong positive causal relationship exists between four explanatory variables (age of household head, access to information, access to credit and degree of vulnerability) and smallholder farmers' agroforestry practicing decision faced with CVC. The study therefore recommends that institutional and socio-economic factors (credit facilities and reliable information) fostering smallholder farmers' practice of agroforestry faced with CVC should be provided by governmental and non-governmental agencies in order to enhance the odds of smallholder farmers practicing agroforestry faced with the adverse effects of CVC.

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