Evaluation of Drought, Wet Events, and Climate Variability Impacts on Maize Crop Yields in East Africa During 1981–2017

East African countries (Uganda, Kenya, Tanzania, Rwanda, and Burundi) experience extreme rainfall phenomena such as droughts, floods, or wet events that usually impact negatively on agriculture. In this regard, the Standardized Precipitation Evapotranspiration Index (SPEI) is employed to assess the occurrence of agricultural drought and wet events based on 3-month and 12-month intervals over the period 1981–2017. Changes in maize yields with rainfall and temperature are analyzed using multi-regression techniques after detrending. The Modified Mann–Kendall test (m-MK) was used to examine the trends in yields and maize production area. The sensitivity index of maize crop yield (MCSI) is expressed as a reduction in maize yields/harvest caused by climate variations or extreme events. The results revealed higher frequencies of drought and wet events in a 3-month SPEI, while a 12-month SPEI presented more distinctive drought and wet events. Most agricultural regions in East Africa (EA) experienced between 43 and 47 months of moderate drought events, 20–23 months of severe droughts, and 11–9 months of extreme drought events during the period 1981–2017. Meanwhile, the wet events of 1997/1998, and 2015/2016 were fully revealed by both 3-month and 12-month SPEI, showing the robustness of SPEI in capturing drought and wet conditions over EA. Statistical crop models revealed that climate variability explained maize yield by approximately 63.0%, 57.0%, 60.0%, 56.0%, and 50.0% for Uganda, Kenya, Tanzania, Rwanda, and Burundi respectively. Except for Rwanda, m-MK showed that maize yields were statistically significantly increasing at a rate of 217.1, 88.9, 143.0, 52.0, and 53.0 kg/ha/year for Uganda, Kenya, Tanzania, and Burundi respectively. MCSI value of 1.0 was revealed in rainfall zone 4, and 0.95 for rainfall zone 5, as compared to 0.85 reported for each of rainfall zones 3 and 8. This implies that the former rainfall zones are more susceptible to extreme drought events or variations than the latter zones. Measures such as irrigation, rainwater harvesting, early warning systems for drought and wet events, and post-harvest handling of crops utilizing drying plates are recommended to adapt to the effects of climate variability.