Evans School Policy Analysis & Research Group (EPAR)

This brief reviews the evidence of realized yield gains by smallholder farmers attributable to the use of high-quality seed and/or improved seed varieties. Our analysis suggests that in most cases, use of improved varieties and/or quality seed is associated with modest yield increases.  In the sample of 395 trials reviewed, positive yield changes accompanied the use of improved variety or quality seed, on average, in 10 out of 12 crops, with rice and cassava as the two exceptions.

This report reviews the literature on textural attributes of Root, Tuber, and Banana (RTB) crops with a focus on studies relevant for crop research and development in Sub-Saharan Africa. The texture of cooked root and tuber crops is often cited as a primary determinant of consumer acceptability of new varieties, including those produced through traditional breeding and through genetic engineering. Evidence from texture-related consumer preferences studies for the RTB crops tropical yam, sweetpotato, banana/plantain, cassava, and potato, as well as the results of physicochemical and genetic studies detailing the current scientific understanding of drivers of textural traits, is reviewed and synthesized.

This report provides a general overview of the market for yams in Ghana. We begin by describing historical trends in yam production and consumption since 1996, recent international trade, and prices. The second section summarizes the varieties grown in Ghana and their uses. The next several sections review available information about the production and marketing systems, followed by a discussion of the importance of yams as a source of nutrition and household income. The limited information available on sweet potato production in Ghana is presented in the appendix. We find that yam production in Ghana has increased steadily over the last 15 years, and that while yam yields have increased from 12.8 MT/Ha in 1996 to 15.6 MT/Ha in 2011, an estimated yield gap of 33.4 MT/Ha persists. Yam export levels have varied over the past 15 years, but show a generally positive trend. Most yam farmers are male smallholders with low levels of education, while most retailers, wholesalers and cross-border traders are women.

This literature review examines the environmental impacts of water buffalo in pastoral and mixed farming systems in Sub-Saharan Africa, South Asia, and South America). The environmental impacts of water buffalo are less widely studied than those of the other livestock species included in this series; typically, the environmental impacts of water buffalo are incorporated into discussions of cattle without more detailed impacts being broken down by bovine type. In Asia and India, where the majority of buffalo are raised, buffalo are typically kept in small herds of only a few animals, which may minimize the local impacts of their grazing on vegetation, soil erosion and water pollution. Some aspects of buffalo feeding and life cycle patterns, as observed in the Amazon, may cause their greenhouse gas emissions to differ from those of cattle: buffalo can fatten on a wider range of grasses, reach market size in a shorter time, transition better from dry to wet seasons, and are more resistant to bovine diseases. While buffalo grazing and trampling can lead to land degradation, buffalo can contribute to nutrient and resource cycling in farming systems because their manure is considered good fertilizer and they can remove and utilize biomass grown on agricultural plots. Mitigation strategies vary by category of environmental impact, but largely suggest improved productivity to reduce land conversion, modified management systems (e.g., biodiversity, water use and consumption, farm and pastures, and waste), and the reduction of livestock numbers altogether.