Closing maize yield gaps in sub-Saharan Africa will boost soil N${}_2$O emissions

In sub-Saharan Africa (SSA), the most important staple crop is maize; the production of which is dominated by smallholder farming systems using low external inputs (<10 kg N ha${}^{-1}$) resulting in low crop yields and large yield gaps (difference between actual and potential yields). To assess increases in soil N${}_2$O emissions when closing maize yield gaps by increased fertilizer use, we reviewed the literature, developed a relationship between yield gaps and soil N${}_2$O emissions, and used it to scale across SSA. According to our analysis, N${}_2$O emissions from maize production will increase from currently 255 to 1755 ± 226 Gg N${}_2$O-N year${}^{-1}$ (+589%) if existing maize yield gaps are closed by 75%, increasing total anthropogenic N${}_2$O emissions for SSA by c. 50%.