Research Topics

EPAR Research Brief #225
Publication Date: 10/15/2013
Type: Literature Review
Abstract

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.

EPAR Research Brief #215
Publication Date: 08/31/2013
Type: Literature Review
Abstract

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.

EPAR Research Brief #213
Publication Date: 08/31/2013
Type: Literature Review
Abstract

 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. 

EPAR Research Brief #216
Publication Date: 08/08/2013
Type: Data Analysis
Abstract

In this brief we analyze patterns of intercropping and differences between intercropped and monocropped plots among smallholder farmers in Tanzania using data from the 2008/2009 wave of the Tanzania National Panel Survey (TZNPS), part of the Living Standards Measurement Study – Integrated Surveys on Agriculture (LSMS-ISA). Intercropping is a planting strategy in which farmers cultivate at least two crops simultaneously on the same plot of land. In this brief we define intercropped plots as those for which respondents answered “yes” to the question “Was cultivation intercropped?” We define “intercropping households” as those households that intercropped at least one plot at any point during the year in comparison to households that did not intercrop any plots. The analysis reveals few significant, consistent productivity benefits to intercropping as currently practiced. Intercropped plots are not systematically more productive (in terms of value produced) than monocropped plots. The most commonly cited reason for intercropping was to provide a substitute crop in the case of crop failure. This suggests that food and income security are primary concerns for smallholder farmers in Tanzania. A separate appendix includes the details for our analyses.

EPAR Research Brief #208
Publication Date: 05/01/2013
Type: Literature Review
Abstract

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.

EPAR Research Brief #212
Publication Date: 03/05/2013
Type: Literature Review
Abstract

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.

EPAR Research Brief #51
Publication Date: 07/02/2009
Type: Research Brief
Abstract

Yam is a major staple in West and Central Africa and an important supplementary food in East Africa. In Sub-Saharan Africa (SSA), virtually all yams are produced for human consumption, with women responsible for processing yams for consumption. This brief provides an overview of the role of women in yam production, and provides a framework for analyzing barriers to women and technology’s impact on women throughout the cropping cycle. We find that though yam was traditionally considered a man’s crop, it is clear that women farmers contribute greatly to yam cultivation, especially during weeding, harvesting, and processing. Propagation of improved varieties with resistance to pests and diseases like yam mosaic disease has great potential to benefit women farmers. Increased yields and lower post-harvest losses will increase household food security.  However, because yams extract high amounts of nutrients from the soil, soil and land management techniques are necessary to ensure future gains in yield. Women’s groups serve as potential venues for dissemination of new yam cultivation and processing technologies.  Additionally, women’s groups can undertake new propagation techniques as income generating activities.  Women farmers need increased extension efforts to fully benefit from technology improvements.

EPAR Research Brief #32
Publication Date: 06/30/2009
Type: Literature Review
Abstract

Though not indigenous to Sub-Saharan Africa (SSA), cassava plays, to varying degrees, five major roles in African development: famine-reserve crop, rural food staple, cash crop for urban consumption, livestock feed, and industrial raw material. Cassava production in SSA was historically a significant staple crop for smallholder farmers and continues to be the second most important food crop in Africa (after maize) in terms of calories consumed. Subsistence crops such as cassava are often considered women’s crops with the standard explanation that women are responsible for feeding the family and thus prefer to grow crops for the household. This brief reviews the role that women play in cassava production, and considers ways to better address gender issues from planting through post-harvest production. We find that the potential gains to cassava production made possible through improved technology will not be fully realized without the participation of women farmers and without women farmers having access to credit, markets, and extension services. Additionally, evidence from SSA suggests that labor for harvesting and processing, rather than labor for weeding, has become the key labor constraint for cassava, and addressing this concern may be more important than further yield increases for raising production levels.

EPAR Research Brief #40
Publication Date: 06/29/2009
Type: Research Brief
Abstract

The millets, a group of small-seeded grasses indigenous to Africa, are an extremely important staple food in resource-poor regions of Sub-Saharan Africa (SSA). Millet requires few inputs, suffers less from insect pests and disease than other grains,  and can tolerate areas even too hot and dry for sorghum.  These characteristics make millet an essential component of food security and risk management strategies for many Africans, though both consumption and production per capita of millet has declined in the last 20 years as farmers have shifted toward maize and rice production. This brief provides an overview of the role of women in millet production, and provides a framework for analyzing barriers to women and technology’s impact on women throughout the cropping cycle. We find that the shift away from millet may result in poorer nutrition and increased time burden for women where they must find alternatives to millet fuel, but that little is known about these consequences. Investing in improved varieties that account for both men’s and women’s preferences, introducing labor-saving technology, and increasing market access all have the potential to increase millet’s production and consumption on the continent. 

EPAR Research Brief #39
Publication Date: 06/05/2009
Type: Research Brief
Abstract

Sorghum grows well in arid and semi-arid agroecological zones and is thus one of the most important cereals in the Sahel region of Sub-Saharan Africa (SSA). Both men and women cultivate sorghum primarily for household consumption, though women are nearly exclusively responsible for post-harvest production of the grain, including brewing and selling sorghum beer.  This brief provides an overview of the role of women in sorghum production, and provides a framework for analyzing barriers to women and technology’s impact on women throughout the cropping cycle. We find that improved sorghum varieties have the potential to greatly increase sorghum yields in SSA by alleviating cultivation threats from striga, pests, and drought.  Because women farmers are the primary cultivators of sorghum, they stand to benefit most from these improved varieties. However, low adoption rates of new technologies suggest that more resources need to be dedicated to extension efforts and informal seed distribution networks that include women farmers. Post-harvest processing of sorghum is both time and labor intensive and is causing many women farmers to transition to maize or rice.  Finally, increased demand for sorghum as a biofuel stock may not translate into gains for women farmers as expected, because women farmers tend to lack input resources, and women farmers often lose control over crops as they transition to cash crops.