Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Biogeosciences, 14, 187-202, 2017
http://www.biogeosciences.net/14/187/2017/
doi:10.5194/bg-14-187-2017
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
12 Jan 2017
Smallholder farms in eastern African tropical highlands have low soil greenhouse gas fluxes
David Pelster1, Mariana Rufino2,3, Todd Rosenstock4, Joash Mango4, Gustavo Saiz5,a, Eugenio Diaz-Pines5, German Baldi6, and Klaus Butterbach-Bahl1,5 1International Livestock Research Institute (ILRI), P.O. Box 30709, Nairobi, Kenya
2Centre for International Forestry Research (CIFOR), P.O. Box 30677-00100, UN Avenue, Nairobi, Kenya
3Lancaster Environment Centre, Lancaster University, Lancaster, LA1 4YQ, UK
4World Agroforestry Centre (ICRAF), P.O. Box 30677-00100, UN Avenue, Nairobi, Kenya
5Karlsruhe Institute of Technology – Institute of Meteorology and Climate Research, Institute of Atmospheric Environmental Research (KIT/IMK–IFU), Kreuzeckbahnstr. 19, 82467 Garmisch-Partenkirchen, Germany
6Grupo de Estudios Ambientales – IMASL, Universidad Nacional de San Luis and CONICET, Ejército de los Andes 950, D5700HHW, San Luis, Argentina
anow at: Department of Life Sciences, Imperial College London, Silwood Park Campus, Buckhurst Road, Ascot, Berkshire, SL5 7PY, UK
Abstract. Few field studies examine greenhouse gas (GHG) emissions from African agricultural systems, resulting in high uncertainty for national inventories. This lack of data is particularly noticeable in smallholder farms in sub-Saharan Africa, where low inputs are often correlated with low yields, often resulting in food insecurity as well. We provide the most comprehensive study in Africa to date, examining annual soil CO2, CH4 and N2O emissions from 59 smallholder plots across different vegetation types, field types and land classes in western Kenya. The study area consists of a lowland area (approximately 1200 m a.s.l.) rising approximately 600 m to a highland plateau. Cumulative annual fluxes ranged from 2.8 to 15.0 Mg CO2-C ha−1, −6.0 to 2.4 kg CH4-C ha−1 and −0.1 to 1.8 kg N2O-N ha−1. Management intensity of the plots did not result in differences in annual GHG fluxes measured (P = 0.46, 0.14 and 0.67 for CO2, CH4 and N2O respectively). The similar emissions were likely related to low fertilizer input rates (≤ 20 kg N ha−1). Grazing plots had the highest CO2 fluxes (P = 0.005), treed plots (plantations) were a larger CH4 sink than grazing plots (P = 0.05), while soil N2O emissions were similar across vegetation types (P = 0.59). This study is likely representative for low fertilizer input, smallholder systems across sub-Saharan Africa, providing critical data for estimating regional or continental GHG inventories. Low crop yields, likely due to low fertilization inputs, resulted in high (up to 67 g N2O-N kg−1 aboveground N uptake) yield-scaled emissions. Improvement of crop production through better water and nutrient management might therefore be an important tool in increasing food security in the region while reducing the climate footprint per unit of food produced.

Citation: Pelster, D., Rufino, M., Rosenstock, T., Mango, J., Saiz, G., Diaz-Pines, E., Baldi, G., and Butterbach-Bahl, K.: Smallholder farms in eastern African tropical highlands have low soil greenhouse gas fluxes, Biogeosciences, 14, 187-202, doi:10.5194/bg-14-187-2017, 2017.
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Short summary
In order to quantify greenhouse gas fluxes from typical eastern African smallholder farms, we measured flux rates every week for 1 year at 59 farms in western Kenya. These upland soils tend to be small sinks for CH4 and small sources of N2O. The management intensity of the farm plots had no effect on emissions, likely because the variability was low. Plots with trees had higher CH4 uptake than other plots. This suggests that emissions from small, low-input farms in this region are quite low.
In order to quantify greenhouse gas fluxes from typical eastern African smallholder farms, we...
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