Pelster, D.E., Rufino, M.C., Rosenstock, T., Mango, J., Saiz, G., Diaz-Pines, E., Baldi, G., Butterbach-Bahl, K., 2015. Smallholder African farms in western Kenya have limited greenhouse gas fluxes. Biogeosciences Discuss. 12, 15301-15336.
Abstract
Few field studies examine greenhouse gas (GHG) emissions from African
agricultural systems resulting in high uncertainty for national
inventories. We provide here the most comprehensive study in Africa to
date, examining annual CO2, CH4 and N2O
emissions from 59 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 fluxes for the GHGs
measured (P = 0.46, 0.67 and 0.14 for CO2, N2O and
CH4 respectively). The similar emissions were likely related
to low fertilizer input rates (≤ 20 kg ha−1). Grazing
plots had the highest CO2 fluxes (P = 0.005); treed plots
were a larger CH4 sink than grazing plots (P = 0.05); while
N2O emissions were similar across vegetation types (P =
0.59). This case 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 inputs, resulted in
high (up to 67 g N2O-N kg−1 aboveground N uptake)
yield-scaled emissions. Improving crop production through
intensification of agricultural production (i.e. water and nutrient
management) may be an important tool to mitigate the impact of African
agriculture on climate change.
