Despite the great potential of agricultural innovations, the uptake by smallholder farmers in sub-Saharan Africa seems to be slow. We reviewed existing theories and frameworks for the uptake of agricultural innovations and found that these tend to emphasize the role of extrinsic factors such as the characteristics of the adopter and the external environment in the decision-making process. In this paper, we argue that intrinsic factors such as the knowledge, perceptions and attitudes of the potential adopter towards the innovation play a key role, but this has been less studied. We present an analytical framework that combines both extrinsic and intrinsic factors in farmers' decisions to adopt new agricultural technologies and apply the framework to agroforestry adoption as a case study. We review the literature on agroforestry adoption in sub-Saharan Africa and identify the extrinsic and intrinsic variables affecting the uptake of agroforestry technologies. We conclude that the uptake of agricultural technologies is a complex process influenced by both extrinsic and intrinsic variables, and recommend that future studies aiming to understand the adoption process of agricultural innovations take into account both sets of variables. A mechanistic understanding of how intrinsic and extrinsic factors interact and drive adoption can help in targeting technologies appropriately to ensure sustainability.
Producing more food for a growing population in the coming decades, while at the same time combating poverty and hunger, is a huge challenge facing African agriculture. The risks that come with climate change make this task more daunting. However, hundreds of thousands of rain fed smallholder farmers in Zambia, Malawi, Niger, and Burkina Faso have been shifting to farming systems that are restoring exhausted soils and are increasing food crop yields, household food security, and incomes. This article reviews these experiences, and their broader implications for African food security, as manifestations of Evergreen Agriculture, a fresh approach to achieving food security and environmental resilience. Evergreen Agriculture is defined as the integration of particular tree species into annual food crop systems. The intercropped trees sustain a green cover on the land throughout the year to maintain vegetative soil cover, bolster nutrient supply through nitrogen fixation and nutrient cycling, generate greater quantities of organic matter in soil surface residues, improve soil structure and water infiltration, increase greater direct production of food, fodder, fuel, fiber and income from products produced by the intercropped trees, enhance carbon storage both above-ground and belowground, and induce more effective conservation of aboveand below-ground biodiversity. Four national cases are reviewed where farmers are observed to be applying these principles on a major scale. The first case involves the experience of Zambia, where conservation farming programmes include the cultivation of food crops within an agroforest of the fertilizer tree Faidherbia albida. The second case is that of the Malawi Agroforestry Food Security Programme, which is integrating fertilizer, fodder, fruit, fuel wood, and timber tree production with food crops on small farms on a national scale. The third case is the dramatic expansion of Faidherbia albida agroforests in millet and sorghum production systems throughout Niger via assisted natural regeneration. The fourth case is the development of a unique type of planting pit technology (zai) along with farmer-managed natural regeneration of trees on a substantial scale in Burkina Faso. Lastly, we examine the current outlook for Evergreen Agriculture to be further adapted and scaled-up across the African continent.
Small-scale farmers in Northern Tanzania grow vegetables that include tomatoes, cabbages and onions and use many types of pesticides to control pests and diseases that attack these crops. Based on the use of questionnaires and interviews that were conducted in Arumeru, Monduli, Karatu, and Moshi rural districts, this study investigates farmers' practices on vegetable pest management using pesticides and related cost and health effects. The types of pesticides used by the farmers in the study areas were insecticides (59%), fungicides (29%) and herbicides (10%) with the remaining 2% being rodenticides. About a third of the farmers applied pesticides in mixtures. Up to 90% had a maximum of 3 pesticides in a mixture. In all cases there were no specific instructions either from the labels or extension workers regarding these tank mixtures. Fifty three percent of the farmers reported that the trend of pesticide use was increasing, while 33% was constant and 14% was decreasing. More than 50 percent of the respondents applied pesticides up to 5 times or more per cropping season depending on the crop. Insecticides and fungicides were routinely applied by 77% and 7%, respectively by these farmers. Sixty eight percent of farmers reported having felt sick after routine application of pesticides. Pesticide-related health symptoms that were associated with pesticides use included skin problems and neurological system disturbances (dizziness, headache). Sixty one percent of farmers reported spending no money on health due to pesticides. These results can be used to develop a tool to quantify the cost of pesticide use in pest management by small-scale vegetable farmers in Northern Tanzania and contribute to the reformation of pesticide policy for safe and effective use of pesticides.
A number of studies have tested the effect of woody and herbaceous legumes on soil fertility and maize yields in sub-Saharan Africa. However, their effects on maize productivity are much debated because results have been variable. A meta-analysis was conducted with the aim of evaluating the evidence in support of yield benefits from woody and herbaceous green manure legumes. A total of 94 peerreviewed publications from West, East and southern Africa qualified for inclusion in the analysis. Maize yield from herbaceous green manure legumes (54 publications), non-coppicing legumes (48 publications), coppicing woody legumes (10 publications), natural fallows (29 publications), and fully fertilized monoculture maize (52 publications) were compared. Mixed linear modelling using yield differences (D) and response ratios (RR) indicated that the response to legumes is positive. The mean yield increase (D) over unfertilized maize was highest (2.3 t ha −1 ) and least variable (CV=70%) in fully fertilized maize, while it was lowest (0.3 t ha −1 ) and most variable (CV=229%) in natural fallows. The increase in yield over unfertilized maize was 1.6 t ha −1 with coppicing woody legumes, 1.3 t ha −1 with non-coppicing woody legumes and 0.8 t ha -1 with herbaceous green manure legumes. Doubling and tripling of yields relative to the control (RR > 2) was recorded in coppicing species (67% of the cases), non-coppicing legumes (45% of the cases), herbaceous green manure legumes (16% of the cases) and natural fallows (19% of the cases). However, doubling or tripling of yields occurred only in low and medium potential sites. Amending post-fallow plots with 50% of the recommended fertilizer dose further increased yields by over 25% indicating that legume rotations may play an important role in reducing fertilizer requirements. Except with the natural fallow, the 95% confidence intervals of D and RR were higher than 1 and 0, respectively indicating significant and positive response to treatments. Therefore, it is concluded that the global maize yield response to legumes is significantly positive and higher than unfertilized maize and natural vegetation fallows.
Low soil fertility is one of the most important biophysical constraints to increasing agricultural productivity in sub-Saharan Africa. Several renewable soil fertility replenishment (RSFR) technologies that are based on nutrient re-cycling principles have been developed in southern Africa. Some success stories have been recorded (e.g. nitrogen-fixing legumes), but the adoption of RSFR technologies has generally lagged behind scientific advances thereby reducing the potential impacts of the technologies. This paper describes the major RSFR technologies being promoted in the region, synthesizes available information regarding their adoption by farmers, and identifies the challenges, key lessons learnt and the way forward for up-scaling RSFR technologies in the region. The review indicated that farmer uptake of RSFR technologies depends on several factors that can be grouped into broad categories: technology-specific (e.g. soil type, management regime), household-specific (e.g. farmer perceptions, resource endowment, household size), policy and institutions context within which RSFR is disseminated (inputs and output prices, land tenure and property rights), and geo-spatial (performance of species across different bio-physical conditions, location of village). Adoption of RSFR technologies can be enhanced by targeting them to their biophysical and social niches, facilitating appropriate policy and institutional contexts for dissemination, understanding the broader context and dynamics of the adoption process, a paradigm shift in the approach to the dissemination of RSFR (e.g. expanding RSFR to high value crop systems, exploring synergy with inorganic fertilizer) and, targeted incentive systems that encourage farmers to take cognizance of natural resource implications when making agricultural production decisions.
The Miombo, the most extensive tropical woodland formation of Africa directly supports the livelihoods of over 100 million people through the provision of many tree products and ecosystem services essential to both the rural and urban communities. While the destruction of the Miombo has often been blamed on the rural communities dwelling near the forest resources, many urban dwellers depend heavily on the various products derived from the woodlands. This paper highlights the importance of the Miombo in the livelihoods of rural people, the potential threats to this ecosystem and opportunities for its sustainable management. About 70% of energy consumed in southern Africa is in the form of fuelwood or charcoal. The economic importance of the Miombo especially from non‐timber forest products (NTFPs) is usually understated due to their perceived non‐economic value yet they play an important role in sustaining livelihoods of forest dependent people in the miombo ecoregion. The Miombo also contributes to health services through the use of medicinal plant and products, in some cases, contributing up to 80% to rural health, including helping in coping with effects of HIV/AIDS, malaria and several diseases. The possibility of developing payment for environmental services schemes through public–private partnerships, and community‐based sustainable management models are proposed. Through conservation and commercialization of some of the products and services, there is a potential to provide income and improve the livelihood of people involved in the trade along the value chain.
In Malawi, N and P deficiencies have been identified as major soil fertility constraints to maize (Zea mays, hybrid NSCM 41) productivity. In this study, we evaluated the effect of three rates of N and P fertilizers on maize performance in monoculture and maize intercropped with the nitrogen fixing legume gliricidia (Gliricidia sepium) in replicated field trials run for four years (2002/03-2005/06 seasons) at Makoka, in southern Malawi. Significant season-to-season variation was found in stand loss, ears per plant, stover yield, grain yield and thousand kernel weight (TKW), which was related to distribution of rainfall received during the growing season. All variables were significantly higher in the gliricidia/maize intercrop compared with monoculture maize. During the four consecutive cropping seasons, grain yields of maize increased by 343% (i.e. from 0.94 tons ha À1 in unfertilized sole maize to 4.17 tons ha À1 in gliricidia/maize intercropping). Optimum synergistic effect on grain yield (38% increase over unfertilized gliricidia/maize) was obtained when half recommended N and P rates were combined with gliricidia indicating interspecific facilitation. Response surface modelling showed that the optimum combination of factors for maximum grain yield (4.2 t ha -1 ) in monoculture maize was 80 kg N ha -1 , 31 kg P ha -1 and 917 mm seasonal rainfall. In the gliricidia/maize intercrop, the stationary point had no unique maximum. Ridge analysis revealed that the estimated ridge of maximum grain yield (5.7 t ha -1 ) in the intercrop is when 69 kg N ha -1 , 37 kg P ha -1 is applied and a seasonal rainfall of 977 mm is received. The total P uptake in the intercrop (14.3 kg ha -1 ) was significantly higher than that in maize monoculture (6.6 kg ha -1 ). P uptake was significantly (P = 0.008) influenced by P fertilizer rate. Therefore, we conclude that combining inorganic N and P fertilizers with organic inputs from gliricidia has positive and synergistic effects on maize productivity in southern Malawi.
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