Soil Greenhouse Gas Fluxes From Maize Production Under Different Soil Fertility Management Practices in East Africa

In sub-Saharan Africa (SSA),
few studies have quantified greenhouse gas (GHG) emissions following
application of soil amendments, for development of accurate national GHG inventories.
Therefore, this
study quantified soil GHG emissions using static
chambers for two maize cropping seasons (one full year) of four
different soil amendments in the central highlands of
Kenya. The four treatments were: (i) animal manure; (ii) inorganic
fertiliser; (iii) combined animal manure and inorganic fertiliser; and (iv) a
no N-control (no amendment) laid out in a randomised complete block design.
Cumulative annual soil fluxes (February 2017 – February 2018) ranged from -1.03±0.19 kg CH4-C
ha-1 yr-1 from the manure inorganic fertiliser treatment
to -0.09±0.03 kg CH4-C ha-1 yr-1 from the manure
treatment, 1391±74 kg CO2-C ha-1 yr-1 from
the control treatment to 3574±113 kg CO2-C ha-1 yr-1 from
the manure treatment and 0.13±0.08 to 1.22±0.12 kg N2O-N ha-1
yr-1 in the control and manure treatments, respectively. Animal
manure amendment produced the highest cumulative CO2 emissions (P<0.001), N2O emissions (P<0.001) and maize yields (P=0.002) but the lowest N2O yield-scaled
emission (YSE) (0.5 g N2O–N kg-1 grain yield). Manure combined with inorganic fertiliser had the highest
cumulative CH4 uptake (P<0.001) and N2O
YSE
(2.2 g N2O–N kg-1 grain yield).
Our results indicate that while the use of animal manure may increase total
GHG emissions, the concurrent increase in maize yields results in reduced yield-scaled
GHG emissions.