N2O-SSA

Fertiliser use in sub-Saharan Africa is currently low, which results in lower agricultural crop yields than in many developed nations. In the coming decades, fertilizer use is predicted to increase, in order to drive increasing agricultural productivity. If fertilizer application is carefully controlled, emissions of greenhouse gases from agriculture soils can be minimized while ensuring high productivity and food security: Climate smart agriculture. The success of climate-smart agricultural practices depends on detailed knowledge of nutrient cycles in soils.

Nitrous oxide (N₂O) is a strong greenhouse gas which makes a large contribution to global warming. In addition, it is the most important substance currently released that contributes to destruction of the ozone layer. N₂O is produced by microbes in soils as they use nitrogen in two key biochemical reactions: Nitrification and denitrification. Agricultural fertilisation increases the amount of nitrogen available in soils, which leads to larger emissions of N₂O. N₂O emissions have primarily been studied in temperate ecosystems, but the causes and magnitude of emissions in sub-Saharan Africa are not well known. Expected changes in N₂O emissions due to climate change and increasing fertilizer use are very poorly constrained, making it particularly difficult to drive investment in climate-smart agriculture in this region.

In this project, we will use a novel measurement technique – laser spectroscopy – to study N₂O emissions from agricultural soils in Kenya. Laser spectroscopy allows us to directly monitor the isotopic composition of N₂O emitted from soils, and thus infer the microbial N₂O production and consumption pathways occurring in the soils. We will monitor N₂O emissions and isotopic composition through a dry-wet seasonal transition to understand how climate and soil moisture control the production of N₂O. We will relate our results to observations of N₂O emissions made at other sites in sub-Saharan Africa, and use machine learning techniques to develop a new model of N₂O emissions. This will allow us to understand and predict emissions and thus contribution to the development and uptake of sustainable agricultural practices.