Frequent droughts and sub-optimal crop management have been identified as the principal constraints on agricultural intensifcation in the Sahel. A new model, the Crop Model for Sahelian Adaptation Studies (CROMSAS), was developed to examine the influence of climatic variability, climate change and crop management strategies on millet yields. To improve the simulation of environmental stresses, several
original features were implemented including a new leaf expansion methodology, semi-independent tillers, stress-dependent partitioning, and intercropping. CROMSAS was designed in a structured, accessible way to facilitate the use of the model by other researchers who want to examine climate change impacts in Africa.
The influences of rainfall and crop management decisions over the period 1950{2009 were assessed for six locations in Senegal with average rainfall from 200mm to 1200 mm. Poor rainfall severely restricted yields in the north of the country in most years while having little impact in the more humid south. In the highly-populated groundnut basin, rainfall variability reduced the effectiveness and hence the profitability of fertiliser application. Current planting densities were found to lie within the optimal range but higher grain yields could have been produced, with lower risk of crop failure, by delaying planting by 2-3 weeks.
The benefits of adapting crop management strategies according to the conditions in previous years were assessed. Using a fixed long-term strategy produced higher long-term yields and profits, at lower risk of crop failure, than frequently changing strategies.
Projections from three GCMs for the period 2000-2100 were converted to daily weather data using a novel methodology and used to examine the impact of climate change on millet cultivation across Senegal. Grain yields were projected to be relatively unchanged for the SRES A2 and B1 scenarios, with losses due to temperature increases and higher vapour pressure deficits being balanced by CO2 fertilisation.
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