Paul W. Heisey

Wheat Rusts and the Costs of Genetic Diversity in the Punjab of Pakistan

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.

An Analytical Model of Farmers' Demand for Replacement Seed

Seed replacement choices differ from decisions about other inputs, such as fertilizer, because the farmer can reproduce seed. Assumptions about rates of improvement in yield potential and depreciation of retained seed are combined with behavioral assumptions and price and technical information to develop a model predicting the number of years before a farmer will buy new seed. Parameter estimates for wheat in Pakistan are fed into the model and results compared with observed replacement times. Time horizon strongly conditions effects of model parameters. To speed varietal change, better information for farmers is likely to be preferred to seed subsidies.

Past and potential impacts of maize research in Sub-Saharan Africa: A critical assessment

Abstract Over the past twenty years, research progress in maize, the single most important food staple in sub-Saharan Africa, has been comparable to progress in other primarily smallholder maize systems in the developing world. Both the number of varietal releases per million hectares of maize and the adoption of improved maize varieties and hybrids are similar to the rates achieved in other regions. This has occurred despite fewer maize breeders per million tons of maize, greater reliance on the public sector, and somewhat more diverse production environments in sub-Saharan Africa. Nonetheless, adoption of improved maize materials has remained patchy, constrained in some cases by failure to incorporate smallholder preferences adequately, and in others by insufficient supporting infrastructure, particularly in development of seed systems. Furthermore, despite an apparently greater investment in crop management research in the region relative to other developing areas, appropriate technology for maintenance of soil fertility in the face of increasing population pressure requires much more attention. This technology will require a combination of both external and internal sources of nutrients. Crop management technology must also be evaluated in terms of effects on seasonal labor demand. Because of the relative diversity in African environments and infrastructural constraints, high-payoff maize technology in sub-Saharan Africa will require particularly careful attention to areas outside maize research itself—policy design, institution building, and human capital development.

Simultaneous estimation of seed-fertilizer adoption decisions: An application to hybrid maize in Malawi

Abstract Simultaneous models are often appropriate for estimating high-yielding variety (HYV) adoption, but most empirical investigations have been based on single-equation models. Using the econometric application of a model for hybrid maize adoption in Malawi as an illustration, this paper argues that researchers investigating HYV innovations need to consider methods for estimating simultaneous censored systems. Further work with associated estimation procedures and diagnostic tests is needed to improve the measurement and prediction of seed-fertilizer adoption.

Gendered impacts of fertilizer subsidy removal programs in Malawi and Cameroon

Gladwins * * 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 Gladwins analysis, men farmers produce hybrid maize and tobacco for export and women produce the subsistence food crop, local maize. Gladwins 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.