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After cereals, root and tuber crops - including sweetpotato and yam (in addition to cassava and aroids), are the second most cultivated crops in tropical countries. This literature review examines the environmental constraints to, and impacts of, sweetpotato and yam production systems in Sub-Saharan Africa (SSA) and South Asia (SA). The review highlights crop-environment interactions at three stages of the sweetpotato/yam value chain: pre-production (e.g., land clearing), production (e.g., soil, water, and input use), and post-production (e.g., waste disposal, crop storage and transport). We find that sweetpotato and yam face similar environmental stressors. In particular, because sweetpotato and yam are vegetatively propagated, the most significant (and avoidable) environmental constraints to crop yields include disease and pest infection transmitted through the use of contaminated planting materials. Published estimates suggest yield gains in the range of 30–60% can be obtained through using healthy planting material. Moreover, reducing pest damage in the field can greatly increase the storage life of root and tuber crops after harvest – currently losses from rot and desiccation can claim up to 100% of stored sweetpotato and yam on smallholder farms.
Maize has expanded through the 20th and into the 21st century to become the principle staple food crop produced and consumed by smallholder farm households in Sub-Saharan Africa (SSA), and maize production has also expanded in South Asia (SA) farming systems. In this brief we examine the environmental constraints to, and impacts of, smallholder maize production systems in SSA and SA, noting where findings apply to only one of these regions. We highlight crop-environment interactions at three stages of the maize value chain: pre-production (e.g., land clearing), production (e.g., fertilizer, water, and other input use), and post-production (e.g., waste disposal and crop storage). At each stage we emphasize environmental constraints on maize production (such as poor soil quality, water scarcity, or crop pests) and also environmental impacts of maize production (such as soil erosion, water depletion, or chemical contamination). We then highlight best or good practices for overcoming environmental constraints and minimizing environmental impacts in smallholder maize production systems. Evidence on environmental constraints and impacts in smallholder maize production is uneven. Many environmental concerns such as biodiversity loss are commonly demonstrated more broadly for the agroecology or farming systems in which maize is grown, rather than specifically for the maize crop. And more research is available on the environmental impacts of agrochemical-based intensive cereal farming in Asia (where high-input maize is a common component) than on the low-input subsistence-scale maize cultivation more typical of SSA. Decisive constraint and impact estimates are further complicated by the fact that many crop-environment interactions in maize and other crops are a matter of both cause and effect (e.g., poor soils decrease maize yields, while repeated maize harvests degrade soils). Fully understanding maize-environment interactions thus requires recognizing instances where shortterm adaptations to environmental constraints might be exacerbating other medium- or long-term environmental problems. Conclusions on the strength of published findings on crop-environment interactions in maize systems further depend on one’s weighting of economic versus ecological perspectives, physical science versus social science, academic versus grey literature, and quantity versus quality of methods and findings.
In this brief we examine the environmental constraints to, and impacts of, smallholder sorghum and millet production systems in Sub-Saharan Africa (SSA) and South Asia (SA). Millet in this paper primarily refers to pearl millet (Pennisetum glaucum), although a number of other millets of significance to smallholder production and food security are also discussed. Sorghum and millets are known for being more tolerant of major environmental stresses including drought and poor soil quality than other major cereals. But water availability is still among the greatest constraints to increased grain production, and soil fertility also significantly limits yields, especially in cases where cultivation occurs on marginal lands and where crop residues are removed for alternative uses. Ultimately sorghum and millets’ relatively higher tolerance to abiotic stresses is expected to promote an increase in global cropping area for sorghum and millets as an adaptation to climate change. Sorghum and millet exhibit relatively few of the environmental impacts commonly associated with more intensively cultivated crops such as fertilizer runoff, pesticide contamination, or water depletion, since both of these crops are overwhelmingly grown by smallholder farmers with few, if any, chemical or irrigation inputs. Nevertheless, the tendency to grow sorghum and millet on marginal and heavily sloped lands does pose some environmental risks – including soil degradation and erosion – that can be mitigated through the adoption of best practices as described in the brief.
Rice is the most important food crop of the developing world and is grown on over 155 million ha worldwide. Food security of the poor, especially in Asia, depends critically on rice availability at an affordable price. In this brief we examine the environmental constraints to, and impacts of, smallholder rice production systems in South Asia (SA) and Sub-Saharan Africa (SSA), noting where the analysis applies to only one of these regions. We highlight crop-environment interactions at three stages of the rice value chain: pre-production (e.g., land clearing), production (e.g., water and other input use), and post-production (e.g., waste disposal). At each stage we emphasize environmental constraints on production (e.g., poor soil quality, water scarcity, crop pests) and also environmental impacts of crop production (e.g., soil erosion, water depletion, pest resistance). We then highlight best or good practices for minimizing negative environmental impacts in smallholder rice production systems. Evidence on environmental issues in smallholder rice production is uneven. Far more research is available for Asian rice production systems, as compared to African rice systems. And with the possible exception of the evidence on water limits to increasing productivity, conclusions on the strength of published findings on crop-environment interactions in rice depends on one’s weighting of economic versus ecological perspectives, physical science versus social science, academic versus grey literature, and quantity versus quality of methods and findings.
This literature review examines the environmental constraints to, and impacts of, wheat production systems in South Asia (SA) and Sub-Saharan Africa (SSA). The review highlights crop-environment interactions at three stages of the wheat value chain: pre-production (e.g., land availability), production (e.g., heat, water, and soil), and post-production (e.g. storage, crop residues, and transport). At each stage we emphasize environmental constraints on production (e.g., poor soil quality, water scarcity, crop pests, etc.) and also environmental impacts of crop production (e.g., soil degradation, water depletion and pollution, greenhouse gas emissions, etc.). We then highlight published best practices for overcoming environmental constraints and minimizing environmental impacts in wheat production systems. We find that wheat is a significant crop that will need to increase production to meet increasing demand. Most land suitable for wheat production is already under cultivation. Improved production methods are needed to address the demand and avert environmental impacts of producing wheat. It should not be assumed that improved varieties alone will be able to realistically address growing demands for wheat. Improved variety seeds should be combined with best practices of improved crop management techniques: optimal planting time, zero tillage, fertilizer management, intercropping, crop residue incorporation, and improved storage techniques.
This desk study reports on the small-scale machinery sector in China and a selection of SSA countries: Ethiopia, Tanzania, Nigeria, Burkina Faso, and Uganda. The report is organized into three sections. Section 1 discusses the current state of small-scale agricultural machinery in SSA for crop and livestock production in each of the SSA countries identified. It also seeks to identify major areas of need in terms of agricultural mechanization and major constraints to agricultural machinery adoption, dissemination and maintenance. Section 2 focuses on the agricultural machinery sector in China and Chinese Africa relationships in agricultural development. It also identifies the major government players in the Chinese agricultural machinery sector. Section 3 is a “directory” of small-scale agricultural machinery manufactured in China with potential relevance for SSA smallholder farmers. We divide machines by function (e.g. threshing) although many Chinese machines are multi-function and can serve multiple purposes. We also note applicable crops, if listed by the manufacturers, and technical specifications as available.
This brief summarizes the literature on caloric and lipid deficiencies and their contribution to nutritional outcomes, and identifies key studies and pieces of literature related to this topic.
As part of the Crops & Climate Change series, this brief is presented in three parts: 1) An evaluation of the importance of wheat in SSA, based on production, net exports, and caloric need, 2) A novel analysis of historical and projected climate conditions in wheat-growing regions, followed by a summary of the agronomic and physiological vulnerability of wheat crops, 3) A summary of current resources dedicated to wheat, based on research and development investments and National Adaptation Programmes of Action. Overall, this analysis indicates that the importance of wheat as an imported product remains high throughout SSA, though food crop production and dependence is concentrated in a relatively small area. Wheat-growing regions throughout SSA are likely to face yield decreases as a result of predicted rises in temperatures and possible changes in precipitation. Resources intended to aid adaptation to climate change flow primarily from public sector research and development efforts, though country-level adaptation strategies have not prioritized wheat.
As part of the Crops & Climate Change series, this brief is presented in three parts: 1) An evaluation of the importance of Sorghum and Millet in SSA, based on production, net exports, and caloric need, 2) A novel analysis of historical and projected climate conditions in Sorghum and Millet growing regions, followed by a summary of the agronomic and physiological vulnerability of Sorghum and Millet crops, 3) A summary of current resources dedicated to sorghum and millet, based on research and development investments and National Adaptation Programmes of Action. Our analysis indicates that sorghum and millets may become increasingly important in those areas of SSA predicted to become hotter and subject to more variable precipitation as a result of climate change. Although sorghum and millet are currently grown on marginal agricultural lands and consumed for subsistence by poorer population segments, climate change could render these drought- and heat-tolerant crops the most viable future cereal production option in some areas where other cereals are currently grown. Fewer international development resources are currently devoted to sorghum and millet than are devoted to other cereal grains, and current resource allocation may not reflect the increased reliance on these grains necessitated by projected climactic changes.
Water is a critical input for significantly enhancing smallholder farmer productivity in Sub-Saharan Africa (SSA) where less than 5% of farm land is irrigated, and in India where 42% of farm land is irrigated. For many years, donors have invested in human-powered treadle pump technologies as a point of entry for smallholder farmers unable to afford motorized pumps. In spite of some successes in treadle pump promotion, however, there is a widespread perception that as soon as smallholder farmers can afford to they quickly transition to motorized diesel- powered pumps. While diesel pumps substantially ease farmers’ workload, they pollute excessively (both in terms of local air quality and greenhouse gas emissions), pump excessive amounts of water, and put farmers at the mercy of cyclical spikes in fuel prices. This brief provides an overview of state-of-the-art alternative energy pumps, including technologies available and implementation lessons learned from China, India, Africa, South America and other regions. Through a literature review, written surveys and phone interviews with water pump producers and non-governmental organizations (NGOs) we evaluate the availability, affordability, and adoption rates of alternative energy technologies in developing countries. Our findings suggest that no single alternative energy water pumping system is a “silver bullet” for rural smallholder irrigation needs. Biofuels may prove a successful short- to intermediate-term solution for farmers who already have access to diesel pumps, but other problems associated with diesel engines, including high maintenance costs and excessive water use remain even when biofuels are used. Solar systems eliminate pollution almost entirely, reduce water consumption, and eliminate the need to purchase fuels. However solar systems are typically prohibitively expensive for smallholder farmers. Wind powered pumping solutions have not proven successful to date, with high costs and irregular wind patterns (either too little or too much wind) proving substantial barriers to widespread adoption.