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Since the 1960s both large- and small-scale Zimbabwean maize farmers have been replacing open pollinated varieties (OPVs) with locally developed hybrids. By the 1990s, most were buying hybrid seed, though the adoption rates of new seed types were slowing. With the collapse of the Zimbabwean economy many small farmers returned to planting OPVs and saving seed, not only because hybrid seed was unavailable but also as a rational response to economic risks. Initially these risks were tied to Zimbabwe's economic structural adjustment programme, which cut extension services, reduced short-term credit and destabilised maize prices. Subsequently risks increased as land invasions on seed producing farms forced the importation of seeds with which small-scale farmers were unfamiliar, and when escalating inflation precluded the use of money as a store of value. Control of inflation, better marketing and restored supplies of local seed should see restored planting of hybrid seed. [ABSTRACT FROM AUTHOR]

Air pollutants often have adverse effects on human health. This paper investigates and ranks a set of policy and technological interventions intended to reduce such health costs in the high population density areas of South Africa. It initially uses a simple benefit–cost rule, later extended to capture sectoral employment impacts. Although the focus of state air quality legislation is on industrial pollutants, the most efficient interventions were found to be at household level. These included such low-cost interventions as training householders to place kindling above rather than below the coal in a fireplace and insulating roofs. The first non-household policies to emerge involved vehicle fuels and technologies. Most proposed industrial interventions failed a simple cost–benefit test. The paper''s policy messages are that interventions should begin with households and that further industry controls are not yet justifiable in their present forms as these relate to the health care costs of such interventions. [Copyright &y& Elsevier]