Types of Research
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Cereal yield variability is influenced by initial conditions such as suitability of the farming system for cereal cultivation, current production quantities and yields, and zone-specific potential yields limited by water availability. However, exogenous factors such as national policies, climate, and international market conditions also impact farm-level yields directly or provide incentives or disincentives for farmers to intensify production. We conduct a selective literature review of policy-related drivers of maize yields in Ethiopia, Kenya, Malawi, Rwanda, Tanzania, and Uganda and pair the findings with FAOSTAT data on yield and productivity. This report presents our cumulative findings along with contextual evidence of the hypothesized drivers behind maize yield trends over the past 20 years for the focus countries.
Common estimates of agricultural productivity rely upon crude measures of crop yield, typically defined as the weight harvested of a crop divided by the area harvested. But this common yield measure poorly reflects performance among farm systems combining multiple crops in one area (e.g., intercropping), and also ignores the possibility that farmers might lose crop area between planting and harvest (e.g., partial crop failure). Drawing on detailed plot-level data from Tanzania’s National Panel Survey, our research contrasts measures of smallholder productivity using production per hectare harvested and production per hectare planted.
An initial analysis (Research Brief - Rice Productivity Measurement) looking at rice production finds that yield by area planted differs significantly from yield by area harvested, particularly for smaller farms and female-headed households. OLS regression further reveals different demographic and management-related drivers of variability in yield gains – and thus different implications for policy and development interventions – depending on the yield measurement used. Findings suggest a need to better specify “yield” to more effectively guide agricultural development efforts.
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.
A farmer’s decision of how much land to dedicate to each crop reflects their farming options at the extensive and intensive margins. The extensive margin represents the total amount of agricultural land area that a farmer has available in a given year (referred to interchangeably as ‘farm size’ or ‘agricultural land’). A farmer increases land use on the extensive margin by planting on new agricultural land. The intensive margin represents area planted of crops as a proportion of total farm size. A farmer increases the intensive margin by increasing output within a fixed area. This analysis examines cropping patterns for households in Tanzania between 2008 and 2010 using data from the Tanzania National Panel Survey (TZNPS). This brief describes changes in farm size, total area planted, and area planted of select annual crops to highlight the dynamic nature of farmer’s cropping choices for a sample population of 2,246 agricultural households that reported having any agricultural land in 2008 or 2010. Throughout the brief, we present summary statistics at the national level and compare them with household-level data to show how results vary depending on how the sub-population is defined and how average measures can mask household level changes. We analyze these questions in the context of smallholders (defined as households with total agricultural land area as less than two hectares) and farming systems.
This report reviews the current body of peer-reviewed scholarship exploring the impacts of morbidity on economic growth. This overview seeks to provide a concise introduction to the major theories and empirical evidence linking morbidity – and the myriad different measures of morbidity – to economic growth, which is defined primarily in terms of gross domestic product (GDP) and related metrics (wages, productivity, etc.). Through a systematic review of published manuscripts in the fields of health economics and economic development we further identify the most commonly-used pathways linking morbidity to economic growth. We also highlight the apparent gaps in the empirical literature (i.e., theorized pathways from morbidity to growth that remain relatively untested in the published empirical literature to date).
Cassava production is prone to many constraints throughout the production cycle, including biotic, abiotic, and management constraints. This brief reviews the literature on the production impacts of two key cassava stressors: cassava bacterial blight (CBB) and postharvest physiological deterioration (PPD). We summarize available estimates of the frequency and magnitude of these constraints relative to other drivers of cassava production losses that affect smallholder farmers in Sub-Saharan Africa (SSA), review the control strategies proposed in the literature, report on the views of several experts in the field, and identify research gaps where relatively little appears to be known about CBB or PPD yield impacts or best practices for CBB or PPD management.
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 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.
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.
This presentation reviews and presents definitions and theories around incorporating sustainability into agricultural productivity. We review ecological, social, and economic sustainability and examine agricultural productivity through the lenses of nutrition, gender, environment, and climate change. The annotated bibliography identifies critical work from academic literature to aid in defining sustainable agricultural productivity. The methodology to generate these reports included searching the University of Washington Libraries system, Google Scholar, the University of Minnesota’s AgEcon Search, as well as the websites of the FAO, World Bank, and CGIAR. We also reviewed the most recent (2010) publications of the Handbook of Agricultural Economics and the Handbook of Development Economics.