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Tropentag, September 20 - 22, 2017 in Bonn

"Future Agriculture: Social-ecological transitions and bio-cultural shifts"

Effect of Manure Quantity and Quality on GHG Fluxes from Tropical Pastures in Kenya

Zhu Yuhao1, Lutz Merbold2, David Pelster2, Eugenio Diaz-Pines3, Klaus Butterbach-Bahl1

1Karlsruhe Institute of Technology, Inst. of Meteorology and Climate Research, Atmospheric Environmental Research, Germany
2International Livestock Research Institute (ILRI), Kenya
3Karlsruhe Institute of Technology, Biogeochemical Processes, Germany


Dung patches on grazed rangeland are a major source of anthropogenic GHGs emissions from agricultural systems. Dung is rich in available carbon and nitrogen, thus, supporting microbial processes such as methanogenesis, nitrification and denitrification. These processes are driving greenhouse gas emissions from dung. However, the amount and quality of dung patches depends on nutritional status and feed intake of the livestock. Factors, which so far have not been considered in most studies focusing on GHG emissions from dung. Moreover, our study focus on Kenya, a country in sub-Saharan Africa (SSA), for which little to nothing is known about regarding manure induced GHG emissions. Using an automated chamber system, we investigated the effect of manure quality and quantity on dung patches' GHG emissions in the dry and wet season. Experiments were done on the campus of the International Livestock Research Institute, Nairobi, Kenya.
While significant CH4 fluxes were observed immediately following dung application to rangelands, no major stimulation of N2O and CO2 fluxes were observed. However, total net GHGs cumulative emissions from 1 kg manure were twice as high as those from 0.5 kg manure during two consecutive dry seasons.
With regard to manure quality experiment, CH4 emissions from farm manure dung patches were approx. one magnitude higher as from dung patches of cattle fed at 40% maintenance. However, no significant manure quality effects were found on both net cumulative CO2 and N2O emissions in four observation periods. Specifically for dung patches N2O emissions showed large variations in total cumulative emissions over a four week period, which could partly be explained by variations in environmental conditions (dry/ wet season), but partly were stochastic. This suggests that more research with more replicates and treatments in different seasons is required to calculate robust emission factors for N2O emissions from dung patches from rangelands in SSA.

Keywords: Dung patches, GHGs emissions, manure quantity and quality, sub-Saharan Africa

Contact Address: Zhu Yuhao, Karlsruhe Institute of Technology, Inst. of Meteorology and Climate Research, Atmospheric Environmental Research, Kreuzeckbahnstr. 19, 82467  Garmisch-partenkirchen, Germany, e-mail: yuhao.zhu@kit.edu

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