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<i>±</i>0.19 kg CH₄-C ha^-1 yr^-1 from the manure inorganic fertiliser treatment to -0.09<i>±</i>0.03 kg CH₄-C ha^-1 yr^-1 from themanure treatment, 1391<i>±</i>74 kg CO₂-C ha^-1 yr^-1 from the control treatment to 3574<i>±</i>113 kg CO₂-C ha^-1 yr^-1 from themanure treatment and 0.13<i>±</i>0.08 to 1.22<i>±</i>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 (<i>P</i>&lt;0.001), N₂O emissions (<i>P</i>&lt;0.001) and maize yields (<i>P</i>=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 CH₄uptake (<i>P</i>&lt;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.