From research to the field: Lessons on N₂O emissions in Sub-Saharan Africa

Author: Turry Ouma

New review paper published

Nitrous oxide (N₂O) is a powerful greenhouse gas, yet its dynamics in agricultural systems across Sub-Saharan Africa (SSA) remain insufficiently characterized. This gap motivated our recently published review paper, The state of cropland nitrous oxide emission research in Sub-Saharan Africa, which brings together evidence from 39 field-based studies across the region. The review shows that N₂O emissions are strongly shaped by fertilizer rates, rainfall, cropping systems, soil types, and how long measurements are taken. We also found that many reported emission factors differ widely from IPCC Tier 1 default values, highlighting the need for emission factors that better reflect SSA’s diverse farming systems. Just as importantly, the review points to major data gaps and shows how differences in study design make comparisons difficult.

Read the paper here.

Distribution of annual N₂O emissions across nitrogen input categories. Boxplots show the median (horizontal line), interquartile range (box), and variability (whiskers), with points representing individual study observations. Sample sizes (n) for each fertilizer rate category are shown above boxplots. Grey points indicate vegetables and tea. See the original paper for further details.

When the research left my desk

Soon after completing the review, we organized an ETH4D-funded stakeholder workshop at the University of Eldoret, Kenya, with the aim of translating scientific evidence on N₂O emissions into policy-relevant insights. The workshop themed Understanding Nitrous Oxide (N₂O) Emissions from Agricultural Soils: Evidence and Implications for Sustainable Farming, brought together policymakers, county-level officials, extension officers, farmers’ representatives, private-sector actors (including fertilizer companies and meteorological services), researchers, and development partners.

Scenes from the workshop, held at the University of Eldoret, Kenya.

The engagement began by establishing a shared foundation through research- and policy-focused inputs. These sessions positioned N₂O emissions within the broader context of climate-smart agriculture in Kenya, while also highlighting the existing fertilizer policy landscape and national climate commitments. Framing the issue in this way emphasized that N₂O emissions are not only a biophysical process, but one shaped by policy decisions, institutional structures, and farmer management choices.

Discussions with farmers and extension officers revealed a clear gap between academic terminology and on-farm realities. Fertilizer use was primarily understood through its role in boosting yields, with limited awareness of nitrogen losses or downstream environmental effects. Addressing this required first unpacking the fate of nitrogen in soils - mineralization, uptake, and losses - before meaningful discussions on N₂O emissions could take place. Even language became a constraint; translating greenhouse gas emissions into Swahili highlighted how poorly defined these concepts remain outside scientific spaces. Subsequent sessions focused on field-based evidence, presenting results on fertilization effects on soil mineral nitrogen and measured N₂O emissions from maize and potato systems in Kenya. These data provided a concrete basis for discussion and helped ground abstract concepts in locally relevant measurements.

The workshop then shifted toward a co-design phase. In mixed stakeholder groups, participants identified key policy messages, priority actions across different time horizons, and barriers and opportunities for the adoption of climate-smart practices. Discussions explored how various actors may contribute to N₂O emissions, how governments and institutions could improve communication, what past interventions had worked or failed, and what conditions might motivate farmers to adopt mitigation measures without compromising productivity.

The workshop brought together a wide range of participants from many different backgrounds to discuss nitrogen fertilization.

Several cross-cutting insights emerged. First, mitigation strategies must align with productivity goals to be considered viable by farmers. Second, extension services play a critical role in translating evidence into practice, but require clearer, context-specific guidance. Third, policymakers emphasized the need for locally derived data and field evidence to support fertilizer policy and climate reporting. Key outputs from the workshop will include a video documentary and a policy brief summarizing the discussions and recommendations, aimed at guiding decision-makers and supporting sustainable, climate-resilient agricultural practices across the region.

Acknowledgements

We would like to thank the SNSF for supporting the N2OSSA project (200021_207348) and the ETH4D program for supporting this workshop.