Multi-scale measurements show limited soil greenhouse gas emissions in Kenyan smallholder coffee-dairy systems
This article (PDF) in the Science of The Total Environment journal aims to quantify soil greenhouse gas (GHG) emissions at different spatial (between farms, among fields within farms, and between fertilised and unfertilised locations within fields) and temporal scales (between seasons, wet and dry periods) in smallholder integrated dairy-coffee systems in Kenya. GHG measurements were carried out for one year, comprising two cropping seasons, using vented static chambers and gas chromatography. Sixty rectangular frames were installed on two farms comprising the three main cropping systems found in the area: 1) coffee; 2) Napier grass; and 3) maize intercropped with beans. Within these fields, chambers were allocated on fertilised and unfertilised locations to capture spatial variability. Results revealed that 66% to 94% of annual GHG fluxes occured during rainy seasons. Furthermore, across the farm plots, coffee received most of the N inputs and had 56% to 89% higher emissions of N2O than Napier grass, maize and beans. Within farm plots, two to six times higher emissions were found in fertilised hotspots – around the perimeter of coffee trees or within planted maize rows – than in unfertilised locations between trees, rows and planting holes. Background and induced soil N2O emissions from fertiliser and manure applications in the three cropping systems were lower than hypothesized from previous studies and empirical models. Advances towards overcoming the dearth of data will facilitate the understanding of synergies and trade/offs of climate-smart approaches for low emissions development in sub/Saharan Africa.