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PurposeThe authors assess the development potential of cowpea beyond grain in local markets in Mali by: (1) identifying trader types and types of cowpea products sold; (2) examining trader roles; (3) estimating gross margins and their determinants; and (4) discussing policy opportunities to further develop the value chain.Design/methodology/approachThe authors analyze data collected through observation and semi-structured questionnaires from 487 sellers in 26 markets, including market, seller, and product characteristics. The authors also calculate gross margins and conduct a regression analysis to identify influential factors.FindingsThe authors identify several types of cowpea sellers in local markets, including processor-retailers, retailers of fresh leaves and fodder, and grain retailers, collectors and wholesalers. Women dominate the marketing of processed products and fresh leaves. The marketing of boiled cowpeas offers retailers higher margin rates compared to fritters and pancakes. Grain sellers, who are mostly men, have lower margins but sell larger quantities. Processor-retailers bring more value to the cowpea value chain. Specialization of the seller in cowpea, regional location of the market and day of the market fair all influence gross margins.Research limitations/implicationsFuture work should explore consumer preferences for different types of cowpea products.Originality/valueThis study of the cowpea value chain in Mali has revealed the multidimensional character of the cowpea plant, which goes far beyond its grain and highlight the important roles played by women.

Inefficient allocation of resources has been documented in West African farming systems where food is produced by extended family farms on multiple plots managed by different members. We revisit this question in Mali by testing fertilizer use and productivity differentials, while introducing soil nutrient measurements as indicators of land quality. In contrast with previous studies, we find little evidence that intrahousehold allocation of fertilizer is inefficient. Gender and generation gaps in productivity persist but lessen as we control for land quality. Findings suggest that women’s fields may be less fertile but may also reflect distinctive objectives and modes of production.

COVID-19 brings new challenges worldwide, including to smallholder farmers and their seed systems. In response, an escalating number of seed projects are being planned to deliver immediate aid or to alter current seed production programs. A Statement, prepared by diverse seed system experts, aims to steer both the immediate aid (next 1–2 seasons) and more developmental planning (next 1–3 years). The Statement includes 10 short-term and 4 medium-term recommendations, placing emphasis on all seed systems smallholders use: formal, informal, and integrated. It also looks beyond seed per se to the direct information and digital systems that shape remote assessments, data sharing and inclusive feedback. The Statement is prefaced by an introduction that helps contextualize the recommendations, reviews the history of humanitarian seed aid and summarizes the varied response forms that have unfolded over the last three decades.

This paper investigates the effects of crop biodiversity on farm income and production risk using a large panel dataset of rural households in Kenya. We consider three different metrics of in situ (on-farm) crop diversification (richness, evenness and concentration). We apply a partial moments-based model to test the effects of each strategy on welfare defined as expected crop income, variability (variance) and downside risk (skewness). Our comprehensive econometric approach differentiates climatic shocks, weather and climate change. The results suggest that the benefits from greater diversification in terms of enhanced land productivity and lower production costs could surpass the foregone benefit from greater efficiency associated with more concentrated production systems. Crop richness and evenness each reduce exposure to crop income risk, especially for more vulnerable farmers who produce below the expected revenue threshold. Farmers who rely on greater crop specialization, on the contrary, are more exposed to crop income risk.

Over a decade ago, the Malian government launched a fertilizer subsidy program to expand fertilizer use, boost productivity, and ultimately, improve food and nutrition security. The program specifically targets key crops in the socio-economic development of Mali: rice, cotton, maize, millet, and sorghum. All farmers of target crops are eligible to obtain subsidized fertilizer at a quantity proportional to the number of hectares they expect to plant to those crops. Subsidy rates differ by crop. We hypothesize that the fertilizer subsidy in Mali changes the agricultural landscape by distorting the incentives to allocate land both among target crops and between target and non-target crops, with unintended consequences for crop diversification. We apply two econometric strategies to a farm household dataset collected in 2017/18 in the most productive agricultural zones of Mali and test the effects of the fertilizer subsidy program on indicators of crop species diversity. Findings from propensity score analysis and control function approaches reveal that the fertilizer subsidy program incites households to allocate more of their land to target crops, resulting in a greater concentration of area in target crops and reduced evenness of the area distribution among them. These findings raise concerns about how best to achieve food and nutrition security, when a costly program such as this favors a non-food crop (cotton) and starchy staples over other nutrient-dense or high value crops. The environmental sustainability of a program that reduces crop species diversity in an agricultural landscape is also questionable.

Purpose Scientists in Pakistan are currently developing biofortified wheat varieties to address widespread zinc deficiency, especially among women and children in poorer rural households. The purpose of this paper is to understand how the productivity and efficiency of small-scale and marginal wheat farmers can be improved so that their households may benefit from zinc-fortified varieties. Design/methodology/approach The authors estimate a stochastic frontier production function model with data from a survey of wheat farmers conducted in Punjab, Pakistan in 2011. Findings The productivities of the newer varieties of wheat were significantly greater than the older varieties, as expected. Farmers growing wheat in the rice-wheat and cotton-wheat zones tend to be more efficient than farmers from the mixed zone. Farmers who wait to adopt a leading variety are not less efficient than earlier adopters, but the longer the time until they switch varieties again, the more inefficient is their wheat production. Older farmers tend to be more technically inefficient than younger farmers, but the effect of education is not statistically significant. Wheat farmers with access to extension advice are more efficient. Farmers whose land suffered from severe salinity or severe toxicity are less productive and less efficient than others. Research limitations/implications The authors find no differences in technical inefficiency effects associated with growing the four most popular varieties, either grown alone or with other varieties – suggesting that no single leading variety should be targeted for biofortification. In contrast to some earlier studies, the authors find that small-scale farmers tend to be less technically efficient. This result underscores the need to specifically target this group in promotional programs, and also to complement these with reinforcement of agronomic recommendations. Originality/value This project is part of the HarvestPlus program to determine the appropriate variety or varieties to biofortify with zinc so that Pakistan’s population can have better health and well-being. Further, the results show that there it is desirable to undertake further studies to improve the productivity and efficiency of wheat farmers in the Punjab, Pakistan to increase the health and well-being of the population in general.

Bt cotton remains one of the most widely grown biotech crops among smallholder farmers in lower income countries, and numerous studies attest to its advantages. However, the effectiveness of Bt toxin, which depends on many technical constraints, is heterogeneous. In Pakistan, the diffusion of Bt cotton occurred despite a weak regulatory system and without seed quality control; whether or not many varieties sold as Bt are in fact Bt is also questionable. We utilise nationally representative sample data to test the effects of Bt cotton use on productivity. Unlike previous studies, we invoke several indicators of Bt identity: variety name, official approval status, farmer belief, laboratory tests of Bt presence in plant tissue, and biophysical assays measuring Bt effectiveness. Only farmer belief affects cotton productivity in the standard production model, which does not treat Bt appropriately as damage-abating. In the damage control framework, all Bt indicators reduce damage from pests. Biophysical indicators have the largest effect and official approval has the weakest. Findings have implications for impact measurement. For policy-makers, they suggest the need, on ethical and productivity grounds, to improve variety information and monitor variety integrity closer to point of sale.

Decades after the Green Revolution, sustaining wheat productivity remains an important policy goal for the government of Pakistan. Understanding the speed of diffusion of new wheat varieties can contribute to this goal. We apply duration analysis to identify the factors that shorten the time until a farmer replaces one modern variety by another, and test hypotheses concerning two recurring themes of the Green Revolution: farm size differences and the role of information sources in seed diffusion. We find that time to adoption averages only 4 years, but is shorter on larger farms. Factors that speed variety change also differ by farm size. Extension and media sources of information significantly influence adoption among larger farmers relative to information gained through social relationships, but this is not the case for marginal farmers. Traits related to consumption quality speed adoption on smaller wheat farms, where families both sell and consume their wheat; higher yields drive adoption for the most subsistence-oriented, marginal group.

The relationship between off-farm work and farm input use in Sub-Saharan Africa has been documented, although results are mixed concerning the direction of effect. Here, we explore the robustness of this linkage by applying a range of econometric models to panel data collected in Kenya, using maize as an example because of its importance as a major food crop among smallholder farmers. We test the relationship between rates of fertilizer use and three types of off-farm earnings (labour on other farms, known as farm kibarua); income from self-employment and informal businesses and earnings from regular employment (salaries, pensions or wages). Consistent with previous research, we find a strong, negative linkage between non-farm work and rates of fertiliser use in maize production, indicating trade-offs in labour allocation and farm investments. However, the relationship between fertiliser use in maize production and earnings from farm kibarua appears to be positive, illustrating the role this type of work can play in easing cash constraints for destitute households. Adding to previous research, model comparisons illustrate the sensitivity of some estimated parameters to modelling assumptions. Further, the application of the general propensity score matching demonstrates that the magnitude of the marginal effects of non-farm income on fertiliser use rates varies as income changes. In the case of non-farm earnings, the response of fertiliser to additional income is negative at lower income levels, but positive at higher levels.

Maize dominates as a staple food in Zambia, where the government has for many years promoted hybrid seed use in order to enhance the food self-sufficiency of poor rural families. Despite the policy importance of household nutrition in Zambia, we are not aware of any recent analyses that have related the use of hybrid seed to diets among smallholder maize growers. Previous research has demonstrated a linkage between indices of dietary diversity and healthy diets among women and children. We estimate two-stage, instrumental variables, Poisson, and ordered logit regression models to test the association between hybrid seed use and four indicators of dietary diversity: food group diversity (24-h), vitamin A diversity (7-day), food frequency (7-day), and frequency of consuming foods fortified with vitamin A (7-day). Results are robust to econometric method and indicator: women interviewed in maize-growing households that plant hybrid seed have more diverse diets.

Research has demonstrated that commercializing smallholder agricultural production is one of the effective ways to boost farmer incomes, employ labor, and stimulate rural economies in Sub-Saharan Africa, but this differs by commodity. We use panel data covering over a decade to estimate output supply functions for smallholder farmers in Kenya, and compare these among three commodities with distinctive product attributes: maize, kale and milk. We find that despite improved market access over the decade, there is little discernible growth in market participation except in the case of milk. A minority of households consistently sell from year to year and market concentration remains high across all the commodities, indicating that production is largely subsistence. Nevertheless, there is greater market orientation and less market concentration in kale and milk than in maize. For all the commodities, market participation is strongly associated with access to land, productive assets, technology use, expected prices and rainfall amount and reliability. We argue that broad-based smallholder market participation can only be realized through interventions that raise smallholder production of marketable surpluses through raising productivity, and this cuts across even the high value sub-sectors such as horticulture and dairy. Also essential alongside such interventions are strategies to improving market access by reducing transaction costs.

We derive input demand functions for fertiliser and hybrid seed, testing for the combined and separate effects of income from non-farm sources and agricultural wage labour among smallholder maize farmers in Kenya. More income from off-farm sources, and specifically non-farm sources, competes with maize intensification, particularly in more productive areas where use rates are higher. In less productive areas, where households rely more on off-farm income and input use in maize is extremely low, agricultural wage labour reduces the likelihood that fertiliser is applied, but when used, has a positive effect on quantities purchased of both seed and fertiliser.

Zambia’s maize seed industry is currently one of the strongest and most competitive in Sub-Saharan Africa. This paper describes the changing structure of the maize seed industry and seed supply chain in Zambia. The aim of the paper is to propose elements of a marketing strategy for seed production and delivery of recently released, provitamin A-rich, orange maize varieties. Information sources include a thorough review of the literature, a statistical survey of farmers in the major maize-producing areas of the country, and key informant interviews conducted with seed company representatives. We discuss the merits of two strategies: (1) liberalizing the provision of original orange maize planting material to all seed companies with the aim of maximizing the impact of this public health intervention, and (2) exclusive rights granted to companies with the goals of preserving differentiated products and ensuring standard seed quality to protect the brand. We find that, exclusive or not, risk-sharing contracts with any company that takes up this product, as well as building and maintaining a unique brand for orange maize would be essential for the success of this product. [EconLit Classifications: Q130, Q160, Q180]. C 2014 Wiley

This paper explores the impacts of hybrid maize adoption on the welfare of farming households in Kenya. We use a four-year panel dataset to estimate the effects of hybrid seed use on four indicators of household welfare, namely, income, assets, inequality and poverty. Results show that use of hybrid seed not only contributes to higher annual income, but also to raising the value of assets, possibly reflecting longer-term welfare effects. Further, we find that use of hybrid seed reduces the depth of poverty, and that the amount planted reduces inequality. As expected, impacts differ between major and minor maize-growing areas of the country. Maize farmers who do not use hybrid seed are clearly disadvantaged. This calls for continued public and private investments in the infrastructure and policy process that supports a competitive, liberalized seed industry and improved access of smallholder farmers to well-adapted, affordable hybrids.

We add to an emerging body of literature on input subsidies in Africa south of the Sahara. Our analysis focuses on demand for seed, characterising smallholders with a high predicted demand for hybrid seed who were not reached by the subsidy programme. We use cross-sectional data from the 2010 agricultural season and an instrumented control function approach to test the hypothesis that the subsidy on hybrid maize seed in Zambia is selectively biased. Consistent with other literature, we find that the subsidy is a recursive determinant of seed demand, but in 2010, its recipients had more land, more assets, and lower poverty rates. Findings illustrate the social costs of the programme as currently designed and highlight the need to build alternative supply channels if poorer maize growers are to grow hybrid seed.

Kenya is a globally recognized maize “success story.” As the overall percentage of maize farmers growing hybrids tops 80% and the seed industry matures, the slow pace of hybrid replacement on farms, and the continued dominance of the seed industry by Kenya Seed Company, may dampen productivity. Our econometric analysis identifies the factors that explain farmer demand for hybrid seed, and the age of hybrids they grow, considering hybrid seed ownership. Male-headed households with more education, more assets, and more land plant more hybrid seed. Scale of seed demand per farm is differentiated by agroecology. We find a strong farmer response to the seed-to-grain price ratio, which we interpret as evidence of a commercial orientation even on household farms. However, despite the dramatic increase in the number of hybrids sold and the breadth of seed suppliers as seed markets liberalize, an older hybrid still dominates national demand.

Although farmers in the Malian Sahel depend on millet for survival, demand and supply constraints have impeded their use of certified seed. We use data collected from households, vendors and seed samples to test the way market purchases of grain and seed affect household food consumption and millet genetic diversity. Purchase of millet grain in markets contributes to food security, but reduces dietary diversity – suggesting that scarce cash was directed toward meeting staple food needs first. Farmers purchased millet grain for seed only in the site with riskier rainfall and smaller market fairs. Although they were more likely to purchase in markets where the genetic dissimilarity of seed was higher, purchasing seed in markets was negatively associated with on-farm diversity. Seed shortage rather than variety experimentation appears to be the motivation for seed purchase. Introducing certified seed in rural markets through small-scale traders will require the provision of market services and promotional efforts.

Maize originated in Mexico, where it is typically grown in association with other crops in themilpasystem. This ancient mode of production is practiced today in ways that vary by cultural context and agro-environment. We use a choice experiment to estimate farmers' valuation of three components of agrobiodiversity (crop species richness, maize variety richness, and maize landraces) in themilpasystem, and examine their interest in cultivating genetically modified (GM) maize. We apply a latent class model to data collected from 382 farm households in the states of Jalisco, Oaxaca, and Michoacán to analyze the heterogeneity of farmer preferences. We identify the characteristics of farmers who are most likely to continue growing maize landraces, as well as those least likely to accept GM maize. Findings have implications for debates concerning the introduction of GM maize and the design ofin situconservation programs in these sites.

We propose an approach to model the derived demand for crop varieties among semi-subsistence farmers in a developing economy, and apply it to smallholder banana producers in Uganda. We model variety planting decisions as being composed of an extensive margin decision to grow a subset of locally available varieties (variety choice); and an intensive margin decision about the scale or extent of variety cultivation per farm (variety demand). We estimate variety demand equations using a more complete representation of the choice set upon which observed planting decisions are made. Computed elasticities of variety demand with respect to variety attributes indicate that the relative importance of consumption and production attributes varies by location and proximity to markets, from which we draw implications for the social and economic impact of crop improvement. The approach that we propose has broad appeal for analysing adoption decisions for modern or traditional varieties of both major and minor crops in developing countries.

"A typical private good is defined by its excludability and rivalry characteristics. Information embodied in a technology might not generate rivalry among its users. By contrast, excludability is certainly a characteristic of this kind of information and its delivery can generate incentives for private participation. This study examines farmers' preferences for seed of new rice varieties and their willingness to pay for seed-related information in villages of Nigeria and Benin. Conjoint analysis is used to estimate the structure of farmers' preferences for rice seed given a set of alternatives. Farmers are considered to be consumers of seed as a production input, preferring one variety over another based on the utility they obtain from its attributes, which depends on their own social and economic characteristics, including whether or not they sell rice. Contingent methods are used to elicit preferences and willingness to pay (WTP) for rice seed. The marginal values of attributes, with and without information about the seed, are estimated with an ordered probit regression. WTP for information is derived from the analysis of WTP for rice seed. The results have implications for the best way to finance research and extension services in the areas of intervention, particularly for new rice varieties. " Authors' Abstract

This research characterizes the biological diversity of millet crops in the semiarid regions of India at the household and village-community ( panchayat) scales of analysis, placing that evidence in the context of local seed systems. A set of seed system parameters that span formal and informal exchange and can be measured empirically are proposed. The analysis is based on data collected through sample surveys of farmers and traders in selected sites of Karnataka and Andhra Pradesh, combined with cultivar taxonomies developed with geneticists and applied to seed samples. Findings demonstrate that millet crop diversity levels at both scales of analysis are significantly influenced by seed system parameters, factors which related studies have omitted. In particular, the presence of active local (formal and informal) seed markets enhances millet richness among and within farming communities. Crop improvement strategies oriented toward local seed markets could provide important benefits and incentives to farm households living in these marginal environments. There is a need, however, for an enhanced theoretical understanding of local seed markets in analyzing crop variety choices and the diversity of materials grown in less favored environments.

This article investigates the effects of wheat genetic diversity and land degradation on risk and agricultural productivity in less favored production environments of a developing agricultural economy. Drawing production data from a household survey conducted in the highlands of Ethiopia, we estimate a stochastic production function to evaluate the effects of variety richness, land degradation, and their interaction on the mean and the variance of wheat yield. Ethiopia is a center of diversity for durum wheat and farmers manage complex variety mixtures on multiple plots. Econometric evidence shows that variety richness increases farm productivity. Variety richness also reduces yield variability but only for high levels of genetic diversity. Simulations with estimated parameters illustrate how planting more diverse durum wheat varieties on multiple plots contribute to improving farmer's welfare.

We predict the potential demand of smallholder farmers for genetically transformed varieties of a food crop, the cooking banana of the East African highlands. Farmer demand for planting material is derived in an agricultural household model that accounts for variety traits and missing markets. The demand for candidate host varieties is predicted using a Zero-Inflated Poisson (ZIP) regression system. The fitted model is used to illustrate the sensitivity of farmer demand for improved planting material to (a) investments in research and development, represented by the effectiveness of gene insertion and expression, and (b) other public investments in education, extension, and market infrastructure that support diffusion. By comparing the characteristics of agricultural households we demonstrate that the choice of host variety can have social consequences, favoring one rural population compared with another. Clients for transgenic banana planting material are likely to be poorer, subsistence-oriented farmers in areas greatly affected by biotic constraints. A model of this type might be useful in assessing the investments needed to support the systematic dissemination of improved planting material. The approach can be generalized to other crop biotechnologies for smallholder farming systems, particularly in developing economies.

Agrobiodiversity is a crucial environmental resource. Much of the agrobiodiversity remaining in situ today is found on the semi-subsistence farms of poorer countries and the small-scale farms or home gardens of more industrialised nations. The traditional farms of Hungary are an example. Labelled “home gardens” as a reflection of their institutional identity during the collectivisation period, they are micro-agroecosystems that provide important functions such as food security and diet quality. This paper applies the choice experiment method to estimate the private benefits farmers derive from four components of the agrobiodiversity found in Hungarian home gardens: richness of crop varieties and fruit trees; crop landraces; integrated crop and livestock production; and soil micro-organism diversity. The analysis is based on primary data collected in three environmentally sensitive areas where pilot agri-environmental programmes have been initiated as part of the Hungarian National Rural Development Plan. Findings demonstrate variation in the private values of home gardens and their attributes across households and regions, contributing to understanding the potential role of home gardens in these agri-environmental schemes. This study has implications for sustaining agrobiodiversity in transitional economies.

Crop landraces contribute to food security and agricultural research that supports productivity or enhances product quality. The few extant landraces still grown in Hungary are found in home gardens, which are subsistence-oriented, small-scale family farms managed with traditional practices. A pluralistic economics methodology was developed to analyse the prospects of including landraces and home gardens in Hungary's National Rural Development Plan. The methodology draws from three fields of economic inquiry: institutional economics, environmental economics and agricultural economics. Data were collected using qualitative and quantitative approaches from over 300 farmers across 22 communities in three regions. This paper summarizes the methodology and highlights its advantages. A synopsis of findings is also reported.

This paper reports the results of a study undertaken to estimate the economic impact in developing countries of efforts by the International Maize and Wheat Improvement Center (CIMMYT) to breed leaf rust resistant spring bread wheat varieties since 1973. The challenge in estimating these benefits lies in the pathogen's ability to mutate to new races, which may infect previously resistant varieties. Genetic resistance, rather than fungicide application, is the principal means of controlling leaf rust in developing countries. Whereas productivity enhancement is often estimated in terms of yield gains and increased supply, productivity maintenance is measured in terms of the yield losses avoided by the research investment. The internal rate of return on CIMMYT's research investment was estimated at 41%. When discounted by 5%, the net present value was US$ 5.36 billion in 1990 dollars, and the benefit-cost ratio was 27:1. These findings emphasise the economic importance of maintenance research in crop breeding programs. © 2003 Elsevier B.V. All rights reserved.

Genetic improvement has been a major contributor to agricultural productivity in the United States, but many questions about the economics of crop breeding, such as the value of pre-commercial germplasm, remain unanswered. This study estimates the marginal value of poorly characterized materials contained in the U.S. national germplasm system. Within the search theoretic framework, we apply a maximum entropy method to estimate the probability and the expected level of improvement in pest susceptibility relative to its best previously observed level. The results indicate that the lower-bound estimate of benefit is significantly higher than the upper-bound cost of conserving an accession. Copyright 2003, Oxford University Press.

In contrast to a perception that ex situ collections of germplasm are rarely used, this empirical case study reveals large numbers of germplasm samples distributed by the US National Germplasm System to many types of scientific institutions located in numerous countries around the world. Germplasm distributions outside the United States favor developing over developed countries in several ways, including the numbers of samples shipped, utilization rates in crop breeding programs, and the secondary benefits brought about through sharing this germplasm with other scientists. Expected future demand is also greater among scientists in developing countries. These findings underscore the importance to global science and technology of retaining such resources in the public domain.

A theoretical model is developed and applied to the search for disease and pest resistance in ex situ collections of wheat genetic resources, employing actual data on frequency distributions, disease losses, and search costs. Experiments developed from case studies clarify several misperceptions about the value of gene banks and their utilization by breeders. The observation that wheat breeders “use” gene banks rarely does not imply that marginal accessions have low value. High costs of transferring genes with conventional breeding techniques mean that it may be efficient to store certain categories of genetic resources (such as landraces) “unused” for many years. Copyright 2000, Oxford University Press.

Recent criticisms of the “green revolution” wheats concern the effects of their popularity on crop diversity and the consequences for productivity and conservation. We use a Just-Pope production function to test the relationship of genetic resource and diversity variables to mean and variance of wheat yields in the Punjab of Pakistan. In irrigated areas, greater area concentration among varieties is associated with higher mean yields. In rainfed districts, genealogical variables are associated positively with mean yield and negatively with yield variance. Further research is needed to overcome data limitations, capture biological relationships more accurately, and specify a fuller decision-making model. Copyright 1998, Oxford University Press.

Two propositions have become common assumptions in the development literature: 1. (a) the Green Revolution caused genetic erosion, and 2. (b) the Green Revolution increased genetic vulnerability. With regard to the first proposition, no causal relationship between the Green Revolution and genetic erosion can be established for bread wheat given the difficulties in measuring genetic erosion and of demonstrating causality. The pattern of genetic variation in farmers' wheat fields has undoubtedly changed over the past 100–200 years with increasing cultivation of varieties released by plant breeding programs, but the implications of these changes for the scarcity of useful genetic resources are unclear. With regard to the second proposition, evidence suggests that since the early years of the Green Revolution, the concentration of wheat area in leading cultivars has declined. The semidwarf wheats of the Green Revolution were also less vulnerable to rust diseases than the tall varieties previously released by plant breeding programs as well as traditional varieties. Although rust diseases continue to pose a challenge to wheat scientists, their understanding of the genetic basis of resistance has increased over time. The percentage of area planted to leading wheat cultivars remains a cause for concern, however, and social scientists need to understand better how various policies affect the spatial distribution of cultivars.

The theory of impure public goods is used to demonstrate why farmers may not grow wheat cultivars with the socially desirable level of rust resistance. First, they may grow cultivars that are high yielding though susceptible to rust. Second, many farmers may grow cultivars with a similar genetic basis of resistance. Expected rust losses can be reduced by (a) more diversified genetic background in released wheat cultivars; (b) greater spatial diversity in planted cultivars; or (c) use of a temporally changing list of cultivars known to be rust resistant. Yield trade-offs associated with these policies illustrate potential costs of increasing genetic diversity. Copyright 1997, Oxford University Press.

We test the hypotheses that subsidies on hybrid seed change maize production, total household income, the severity of poverty, and relative deprivation among smallholder maize growers in Zambia. The analysis contributes to the literature by measuring the quantitative effects of seed (as compared to fertilizer) subsidies on indicators of household well-being rather than input demand. We apply a combination of econometric approaches to a nationally representative, balanced panel of smallholder maize-growing households, and invoke the chain rule to generate quantitative estimates of impacts per kilogram of subsidized seed. Our findings demonstrate that in the initial years of the program, subsidized seed enhanced the well-being of smallholder maize growers according to each indicator, but by small magnitudes. Simple calculations suggest high private and social benefit-cost ratios when benefits are measured in terms of household income, although magnitudes are sensitive to seed price and administrative costs.

The pattern of maize seed development in Malawi demonstrates the importance of farmers' capacity to articulate their interests through collective action and institutions. Despite the vital significance of maize as a wage good in Malawi, limited effective demand for maize seed research prolonged the period of technical stagnation. Analysis of the institutional factors shaping the demand for maize seed research complements previous work on Malawi's political economy, the supply of seed technology and adoption, with implications for current political changes in that nation, the importance of farmers' organizations, and state commitment to agricultural research in sub-Saharan Africa.

Farmer adoption of seed/fertilizer technology can be characterized in terms of several interrelated choices. One choice is whether to adopt only seed, only fertilizer, or both components of the technology (adoption). Another choice relates to the extent of land allocation to modem and to farmers' seed varieties (extent of adoption). A third choice is the level per hectare of either seed or fertilizer or both (intensity of adoption).1 In the literature about agricultural innovations in developing countries, some theoretical models treat more than one aspect of the adoption decision,2 but most econometric approaches have portrayed only the discrete adoption choice for a single input. Although farmers often adopt parts or components of recommended technology, neither the theoretical nor the econometric models have included the level of fertilizer applied to farmers' varieties in the analysis of seed/ fertilizer adoption.3 Two features of the seed/fertilizer adoption decision, as defined above, are particularly evident in Malawi. First, even when farmers adopt hybrid maize, they continue to allocate a part of their maize area to their own varieties. Microeconomic theory provides four explanations for land allocation to both modern and traditional seed variet

Microeconomic theory provides four competing explanations for partial land allocation to new and traditional seed varieties in HYV adoption decisions: input fixity, portfolio selection, safety-first behavior, and learning. Testing a general model that contains each as a special case suggests that they are jointly most likely to explain land allocation in the HYV adoption decisions of Malawian smallholders. Yet when each explanation is tested to the exclusion of the others (as is usually the case in the literature), competing hypotheses are individually significant. Results suggest that employing approaches based on single explanations may lead to inappropriately narrow conclusions.

Gladwin's ∗∗ main contention is that women provide most of the agricultural labor in sub-Saharan Africa and because much of this labor is oriented to food production for home consumption, the effects of structural adjustment programs on them and the children they work to feed are likely to be different than on men who produce crops for commercial and export production. Her specific hypothesis for Malawi is that the removal of the fertilizer subsidy affects women farmers more than men farmers because it reduces fertilizer use on local maize. As part of the structural adjustment program, a major purpose of removing the fertilizer subsidy is to reallocate resources from food production for domestic consumption to cash crop production for export. In Gladwin's analysis, men farmers produce hybrid maize and tobacco for export and women produce the subsistence food crop, local maize. Gladwin's main contention is probably correct. For the Malawi case, the presentation does not support the hypothesis because two of the major underlying assumptions are inappropriate and the evidence provided is inconclusive. This comment proceeds by discussing the two assumptions and corresponding evidence. The purpose of this comment is not to contradict the hypothesis, but to clarify the Malawi situation and to suggest that a different analytical approach is needed in that context.

Agricultural innovations are often promoted as a package-a new seed variety, a recommended fertilizer application, and other recommended cultivation practices. Nevertheless, many farmers adopt pieces of the package rather than the whole, in a sequential fashion. This paper presents a behavioral model which explains sequential adoption as a consequence of learning by adopting farmers. In order to learn more about the entire technological package, the farmer may adopt a part of the package. The model is shown to be consistent with observed patterns of sequential adoption.

We hypothesize that institutions such as agricultural cooperatives influence regional levels of variety diversity through input supply, processing or marketing functions. This diversity can also affect yield, a partial measure of crop productivity. We test these hypotheses with data from southern Italy, a mega-diversity spot and centre of diversity for durum wheat. Cooperatives in the southern regions of Italy process farmers’ harvests of durum wheat into bread, label it, and sell it locally. In this relatively marginalized region of the country, cooperatives enable farmers to capture more of the value of the final product and reduce marketing costs. To test the hypothesis, we apply a two-stage estimation approach with a Cobb-Douglas production function and panel data analysis. Findings suggest that the density of cooperatives in a region is associated with greater spatial diversity in wheat varieties grown, and that, over a 14-year period, this diversity positively affected crop yields.

"This paper presents an empirical case study about farmer management of rice genetic resources in two communities of Nepal, drawing on interdisciplinary, participatory research that involved farmers, rice geneticists, and social scientists. The decision-making process of farm households is modeled and estimated in order to provide information for the design of community-based conservation programs. A bivariate model with sample selection treats the simultaneous process of whether farmers decide to plant landraces or modern varieties, and whether the landraces they choose to plant constitute genetic diversity of interest for future crop improvement. Findings show that the two landrace choices are affected by different social and economic factors. The estimation procedure demonstrates that in certain cases, however, the decision processes are interrelated. Policies to promote the conservation of local rice diversity will need to take both processes into account. Fitted equations are then used to compare the likelihood that households targeted for conservation according to one set of conservation criteria also meet other conservation criteria. Households most likely to plant landraces identified as important for crop improvement also grow richer, more spatially diverse rice varieties. In these communities, few policy trade-offs would result from employing one set of criteria instead of the other." Authors' Abstract

Conventional methods were used to assess the benefits and costs of an unconventional project whose purpose was to test whether participatory crop improvement can encourage Mexican farmers to continue growing maize landraces by enhancing their current use value. Findings suggest that farmers as a group earned a high benefit-cost ratio from participating, though from the perspective of the private investor the returns were low. The project also generated social benefits, but these would be difficult (and costly) to measure. There was a gender bias in both participation and benefits distributions, though there is some evidence of a welfare transfer to maize deficit households. Application of other valuation approaches will be necessary in order to assess both the private and social benefits of similar projects. © 2003 Elsevier B. V. All rights reserved.

The principal advantage of in situ conservation is that it allows adaptive evolutionary processes to continue in the species that are being conserved. For a cultivated crop species, in situ conservation involves farmers' management of their own genetic resources even as the farmers themselves adapt to a changing environment. Improved seed selection practices and other on-farm breeding strategies have been proposed as a means of providing economic incentives for farmers to continue growing traditional varieties or landraces identified as important for conservation. This paper describes a pilot study among a group of indigenous farmers in the Sierra de Santa Marta, Veracruz, Mexico, who have collaborated in such efforts. The findings raise key issues about the potential impact of such an approach, as well as some useful methodological points for applied economists. In the study area, there is a high frequency of experimentation, exchange, loss, and replacement of seed over time -- seed of the same varieties, including both modern and traditional varieties. This poses a challenge for economists' models of varietal choice, which tend to be based on static perceptions of a 'variety' as well as simplistic distinctions between 'modern' and 'traditional' varieties. Seed selection in the study area is not a single event but an iterative, continuous process. Women may be more involved in seed selection than previously thought, which may have implications for the welfare impact of new seed selection practices. Other implications of the study are that (1) the impact of introducing practices to enhance farmers' varieties is likely to be diffuse and difficult to observe, predict, or measure, and (2) in developing analytical models of farmer decision-making as it affects the diversity of genetic resources on the farm, the most appropriate unit of analysis for predicting the effects of some policy interventions is not likely to be the individual farmer or the individual farm household. A better understanding of the 'social infrastructure' shaping seed and information flows is needed, since in the diffusion of innovations of this type, the seed system is based entirely on farmers and their interactions.

Variety change and genetic diversity are important means of combating crop losses from pests and diseases in modern agricultural systems. Since the Green Revolution, genetic diversity among wheat varieties released in India has increased but variety change on farms continues to be slow. In this article, we define and summarise indices of variety change and genetic diversity for the wheat varieties released and grown in Indian Punjab during the post-Green Revolution period. We evaluate the effect of each index on technical efficiency with a Cobb-Douglas yield model after testing for exogeneity. Findings support the hypothesis that slow variety change has offset the positive productivity effects of diversifying the genetic base in wheat breeding during the post-Green Revolution period. Policies that speed the rate of variety change and contribute to a more equitable spatial distribution of modern varieties could support wheat productivity in the Punjab of India, reinforcing plant breeding successes.