Modelling climate change impacts on maize yields under low nitrogen input conditions in sub‐Saharan Africa

Abstract

Smallholder farmers in sub‐Saharan Africa (SSA) currently grow rainfed maize with limited inputs including fertilizer. Climate change may exacerbate current production constraints. Crop models can help quantify the potential impact of climate change on maize yields, but a comprehensive multimodel assessment of simulation accuracy and uncertainty in these low‐input systems is currently lacking. We evaluated the impact of varying [CO2], temperature and rainfall conditions on maize yield, for different nitrogen (N) inputs (0, 80, 160 kg N/ha) for five environments in SSA, including cool subhumid Ethiopia, cool semi‐arid Rwanda, hot subhumid Ghana and hot semi‐arid Mali and Benin using an ensemble of 25 maize models. Models were calibrated with measured grain yield, plant biomass, plant N, leaf area index, harvest index and in‐season soil water content from 2‐year experiments in each country to assess their ability to simulate observed yield. Simulated responses to climate change factors were explored and compared between models. Calibrated models reproduced measured grain yield variations well with average relative root mean square error of 26%, although uncertainty in model prediction was substantial (CV = 28%). Model ensembles gave greater accuracy than any model taken at random. Nitrogen fertilization controlled the response to variations in [CO2], temperature and rainfall. Without N fertilizer input, maize (a) benefited less from an increase in atmospheric [CO2]; (b) was less affected by higher temperature or decreasing rainfall; and (c) was more affected by increased rainfall because N leaching was more critical. The model intercomparison revealed that simulation of daily soil N supply and N leaching plays a crucial role in simulating climate change impacts for low‐input systems. Climate change and N input interactions have strong implications for the design of robust adaptation approaches across SSA, because the impact of climate change in low input systems will be modified if farmers intensify maize production with balanced nutrient management.

COVID-19 and food security in Sub-Saharan Africa: implications of lockdown during agricultural planting seasons

“…While SSA countries have very high potential for maize and rice production (Fig. 2), the impacts of climate change [44][45][46] and recent locust invasion 47,48 coupled with COVID-19 movement restrictions are likely to reduce the production potential 49 . Fig.…”

Climate Change Impact and Variability on Cereal Productivity among Smallholder Farmers under Future Production Systems in West Africa

“…Thus, investments into crop production are likely to yield lower benefits under USDP than under SDP, in spite of the relatively higher yield increases. The more intensified smallholder systems become, the higher the impact of climate change [9,36]. The positive yield gains expected from CO 2 fertilisation were generally offset by the higher temperature effect on plant growth, hence resulting in low grain yields.…”

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

“…Yn will decline by 16-41% compared to 15-36% reduction expected for Yp and Yw. The slightly higher reduction in Yn is due to a climate induced reduction in NUE given that more rainfall and higher temperatures enhance risks for N losses via volatilization and leaching (Falconnier et al, 2020). Furthermore, water de cits coupled with increased temperatures lead to lower nitrogen uptake and crop yield (Liang et al, 2018).…”

“…Optimizing management practices including fertilizer application has potential to mitigate the impacts of climate change on maize yields. For instance split fertilizer application and manure application can improve both NUE and yields (Falconnier et al, 2020;Liang et al, 2018).…”