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

Authors: FALCONNIER, G. - University Of Montpellier; COREELS, M. - International Maize & Wheat Improvement Center (CIMMYT); BOOTE, K. - University Of Florida; AFFHOLDER, F. - Agriculture Research And Development Service (SERIDA); ADAM, M. - Leibniz Centre; RUANE, A. - National Aeronautics And Space Administration (NASA); Ahuja, Lajpat; Anapalli, Saseendran; BARON, C. - University Of Montpellier; BASSO, B. - Michigan State University; BAUDRON, F. - International Maize & Wheat Improvement Center (CIMMYT); BERTUZZI, P. - Institut National De La Recherche Agronomique (INRA); Timlin, Dennis

Submitted to: Global Change Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/6/2020
Publication Date: 7/6/2020
Citation: Falconnier, G.N., Coreels, M., Boote, K.J., Affholder, F., Adam, M., Ruane, A.C., Ahuja, L.R., Anapalli, S.S., Baron, C., Basso, B., Baudron, F., Bertuzzi, P., Timlin, D.J. 2020. Modelling climate change impacts on maize yields under low nitrogen input conditions in sub-Saharan Africa. Global Change Biology. 1-48. https://doi.org/10.1111/gcb.15261.
DOI: https://doi.org/10.1111/gcb.15261

Interpretive Summary: An international project was launched in 2010 to foster increased global collaboration among agricultural scientists to improve different models used as tools for developing agricultural management decision support systems. The current study evaluated the impact of different climate conditions (levels of carbon dioxide, temperature, and rainfall amounts) on corn yield with different fertilizer inputs in five various environments in sub-Saharan Africa using 25 previously established global models. One of USDA-ARS's own models (RZWQM) was used in this study. With improvements made to this model, more reliable support tools for agricultural water management in the Mississippi Delta can be established.

Technical Abstract: Smallholder farmers in sub-Saharan Africa (SSA) currently grow rainfed maize with limited inputs including fertilizer. Maize is crucial for food security in SSA, and climate change may exacerbate current production constraints. Crop models can help quantify the potential impact of climate change on maize yields in these low-input systems. 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-1) for five environments in SSA, including cool sub-humid Ethiopia, cool semi-arid Rwanda, hot sub-humid Ghana and hot semi-arid Mali and Benin using an ensemble of 25 maize models. Models were (i) calibrated with measured grain yield, plant biomass, plant N, leaf area index (LAI), harvest index and in-season soil water content from two-year experiments in each country, (ii) evaluated for their ability to predict observed yield and (iii) tested for their responses to climate change factors. Calibrated models reproduced measured grain yield variations well with average rRMSE of 26%. Nitrogen fertilization controlled the response to variations in [CO2], temperature and rainfall. Under no N fertilizer input (0 kg N ha-1), maize (i) benefited less from an increase in atmospheric [CO2], (ii) was less affected by higher temperature or decreasing rainfall and (iii) was more affected by increased rainfall compared with N fertilizer inputs (80, 160 kg N ha-1). The model inter-comparison revealed that simulation of daily N supply and N leaching plays a crucial role in simulating climate change impacts for low-input systems. More field experiments are needed to advance our understanding of climate change and N input interactions. These interactions have strong implications for the design of robust adaptation practices across SSA, as farmers who intensify maize production with increased use of mineral fertilizer are likely to be affected differently by climate change.