Climate change and increased climate variability are currently seen as the major constraints to the already stressed smallholder farming livelihood system in Southern Africa. The main objectives of this study were first to understand the nature and sources of vulnerability of smallholder farmers to climate variability and change, and second to use this knowledge to evaluate possible farm-level management options that can enhance the adaptive capacity of smallholder farmers in the face of increased climate variability and long-term change in climate.
The long-term rainfall and temperature analyses closely supports farmers’ perceptions that the total annual rainfall has so far not changed, but variability in the rainfall distribution within seasons has increased. The temperature increased in the range 0.2-0.5°C per decade, over the period from 1962 to 2000 and is set to increase significantly in future.
The impacts of rising temperatures and increased rainfall variability among smallholder households were highly differentiated because different households depend on varied farming livelihood sub-systems, which were exposed uniquely to aspects of climatic risk.
Experimentation in this study demonstrated that the maize cultivars currently on the market in Zimbabwe, and in many parts of Southern Africa, exhibit narrow differences in maturity time such that they do not respond differently to prolonged dry spells. With climate change none of the available cultivars will be able to compensate for the decline in yield. Poor soil fertility constrained yield more strongly than rainfall and late planting, as demonstrated by the large yield gap (> 1.2 t ha-1) between the unfertilized and fertilized cultivars even in the poor rainfall season (2010/2011). Maize yielded more than finger millet and sorghum even in the season with poor rainfall distribution. Finger millet and sorghum failed to emerge unless fertilizer was applied.
Small grains for maize
The better performance of maize over finger millet and sorghum suggested that the recommendation to substitute small grains for maize as a viable adaptation option to a changing climate, will neither be the best option for robust adaptation nor attractive for farmers in southern Africa. The maize response to mineral nitrogen is, however, projected to decline as climate changes, although effects only become substantial towards the end of the 21st Century. Overall, soil fertility management is therefore likely to be a major entry point for increasing the adaptive capacity of smallholder farmers to climate change and increased climate variability.