A Dissertation Submitted in Partial Fulfillment of the Requirements for the Degree of
Doctor of Philosophy in Life Sciences of the Nelson Mandela African Institution of
Science and Technology
Land use systems, mainly, crop farming is among the leading sources of greenhouse gas
emissions into the atmosphere, driving climate variability and global warming. This study
aimed to compare greenhouse gas fluxes and crop yields from various land use systems in
Wakiso District, Uganda. Specifically, the study; (a) assessed soil physical-chemical
properties and greenhouse gas fluxes from land use systems, (b) determined the effect of
cropping systems and management practices on greenhouse gas fluxes and crop yields, and
(c) assessed the effect of precipitation, soil temperature, and elevation on greenhouse gas
fluxes. Greenhouse gas fluxes and crop yields were monitored under split-plot design
experiments. Digital gas meters and static chambers were used to measure greenhouse gas
fluxes. Carbon dioxide fluxes were highest and lowest in sole cropped sweet potatoes under
non-mulched deep tillage (148.12 ± 3.40 µg C m−2 hr−1
) and grasslands (53.03 ± 1.70 µg C
m−2 hr−1
), respectively. Nitrous oxide fluxes were highest and lowest in sole cropped beans
under non-mulched reduced tillage (14.21 ± 0.40 µg N m−2 hr−1
) and banana-coffee intercrops
under compost - reduced tillage (3.76 ± 0.20 µg N m−2 hr−1
), respectively. Methane uptake
was highest and lowest in banana-coffee intercrops under mulched - no-tillage (-0.57 ± 0.00
µg C m−2 hr−1
) and sole cropped sweet potatoes under mulched - no-tillage (0.3 ± 0.01 µg C
m−2 hr−1
), respectively. Crop yields were slightly higher in intercropped than sole cropped
systems. Carbon dioxide fluxes were highest and lowest at 1200 - 1340 m (87.42 ± 5.60 µg C
m
−2 hr
−1
) and 900 - 1000 m (52.41 ± 3.90 µg C m−2 hr
−1
), respectively. Nitrous oxide fluxes
were highest and lowest at 1200 - 1340 m (6.82 ± 0.80 µg N m
−2 hr
−1
) and 900 - 1000 m (3.65
± 0.60 µg N m
−2 hr
−1
), respectively. Methane flux was highest at 1200 - 1340 m (0.31 ± 0.01
µg C m−2 hr
−1
) and lowest at 900 - 1000 m (0.04 ± 0.00 µg C m−2 hr
−1
). The results are vital in
understanding greenhouse gas fluxes and crop yields from various land use systems in
Uganda