Abstract

Many studies have dealt with crop production under climate change projections in sub-Saharan Africa, focusing on average long term trends over time-windows of five to twenty years. The efforts undertaken in this study rather combine effective farm management/abiotic factors (e.g., soil tillage, sowing date, fertilizer use, soil fertility status) with variabilities in rainfall conditions at decadal scale to simulate rainfed maize yield in Benin (West Africa). To achieve this goal, the model system Environmental Policy Integrated Climate (EPIC) was used. Management options such as fertilizer use and sowing date scenarios were considered. Variability in rainfall conditions were considered to account for extremes in yield production. Changes in plant growth limiting factors such as water stress and nitrogen stress were conjointly analyzed to account for not only the effects of climate changes, but also soil fertility status and various pressures on the land resources. Excluding catastrophic factors such as floods and pests the results indicate yield production ranges of about 500 to 1400 (±250) kg ha^-1 a^-1 in the North and 1100 to 2300 (±300) kg ha^-1 a^-1 in the South of the investigated region. The impacts of sowing date on the production were within comparable magnitudes of that of climate changes/ rainfall variability (up to -50% of the yield in the North). Higher yield production was globally associated with earlier sowing date referring to the period 2000 to 2009, while associated with later sowing dates referring to period 2010-2050. Moreover, higher water stress is associated with earlier sowing dates, while higher nitrogen stress is associated with later sowing dates referring to the period 2010 to 2050. Shifting towards late sowing dates corresponding to a cumulated rainfall of 180 mm may reduce water stress and make efficient use of fertilizers in future (2010 to 2050), regardless high or low annual rainfall.

Key words: Maize yield, sowing date, fertilizer use, rainfall variability, climate change impacts.