Improving nitrous oxide (N₂O) emissions accounting in Kenya: Insights and measurement results relating to fertilizer practices, environmental drivers, and N isotopic composition

The use of mineral fertilizers in Sub-Saharan Africa (SSA) is crucial for enhancing agricultural productivity but also raises concerns about emissions of nitrous oxide (N₂O), a potent greenhouse gas. Despite their importance for agriculture, N₂O emissions remain poorly understood in SSA, limiting the development of accurate emissions inventories and the adoption of climate-smart agricultural practices.

In the N2O-SSA project, we quantified N₂O emissions from maize and potato cropping systems under nitrogen application rates of 50 kg N/ha and 100 kg N/ha, compared to control plots, using automated static chamber methods. Fertilizer treatments included urea and triple superphosphate (TSP), and control plots received no nitrogen. Preliminary results showed significant temporal and treatment-specific variability in N₂O emissions, with peaks following fertilizer applications and rainfall events, highlighting the interaction between nitrogen availability and soil moisture. Cumulative annual N₂O emissions were found to vary widely depending on nitrogen application rates and crop types, with fertilizer treatments driving the majority of emissions. Emission factors (EFs) were within ranges consistent with previous studies, highlighting differences between crops such as maize and potatoes. Control plots consistently showed negligible emissions, underlining the critical role of nitrogen inputs in driving N₂O fluxes.

These findings underline the importance of crop-specific nitrogen dynamics in shaping N₂O emissions, and the need for tailored nitrogen management strategies to balance agricultural productivity with environmental sustainability. In the next phase of the project, we will analyze soil samples for N₂O isotopic composition, measuring δ¹⁵N-NH₄ and δ¹⁵N-NO₃, in addition to analyzing gas samples to provide further insights into the sources of N₂O emissions. This will inform more efficient nitrogen management practices for sustainable agricultural systems in Sub-Saharan Africa.