Climate change impacts on rainfed maize yields in Zambia under conventional and optimized crop management

Abstract Maize production in Zambia is characterized by significant yield gaps attributed to nutrient management and climate change threatens to widen these gaps unless agronomic management is optimized. Insights in the impacts of climate change on maize yields and the potential to mitigate negative impacts by crop management is currently lacking for Zambia. Using five Global Circulation models and the WOFOST crop model, we assessed expected climate change and the impacts on maize yields at a 0.5° × 0.5° spatial resolution for RCP 4.5 and RCP 8.5 scenarios. Impacts were assessed for two future periods (i.e. near future: 2035–2066 and far future: 2065–2096) in comparison with a reference period (1971–2001). The average surface temperature and summer days (above 30°C) are projected to increase strongly in the southern and western regions. Precipitation is expected to decline, except in the northern regions while the number of wet days decline everywhere, indicating a shortening growing season. The risk of crop failure in western and southern regions increases due to dry spells and heat stress while crops in the northern regions will be threatened by flooding or waterlogging due to heavy precipitation. The simulated decline in the water limited and water- and nutrient- limited maize yields varied from ca 15–20% in the near future and from ca 20–40% in the far future, mainly due to the expected temperature increases. Optimizing management by adjusting planting dates and maize varieties can counteract these impacts by 6–29%. Quantitatively, the existing gaps between water limited yields and nutrient limited maize yields are substantially larger than the expected yield decline due to climate change. Improved nutrient management is therefore crucial to avoid crop yield decline and might even increase crop yields in Zambia.