Seasonal Effluxes of Greenhouse Gases Under Different Tillage and N Fertilizer Management in a Dryland Maize Mono-crop

There are few studies that have assessed greenhouse gas (GHG) effluxes under dryland agriculture, especially in South Africa. Subsequently, limited data in the sub-Saharan region impedes the formulation of policies on GHG mitigation and adaptation. Therefore, the need to study effluxes of carbon dioxide (CO 2 ), nitrous oxide (N 2 O) and methane (CH 4 ) was salient. The objective of the study was to assess GHG effluxes across seasons in conventional tillage (CT) and no-till (NT) systems under nitrogen (N) fertilizer management. Gases were sampled using static PVC chambers and sampling was done by inserting a 25-mL polypropylene syringe into the chamber septa and slowly removing the gas. Samples were analysed for CO 2 , CH 4 and N 2 O using gas chromatography. In winter, CH 4 effluxes were higher under NT than CT for each application rate ( p < 0.05). N 2 O efflux was higher ( p < 0.05) under CT at 120 and 240 kg N ha −1 compared to NT in summer. The CO 2 effluxes of CT were higher ( p < 0.05) than NT at all N application rates and seasons. Higher GHG effluxes in summer than winter was attributed to higher soil temperature and moisture. CO 2 and N 2 O emissions were positively correlated to tillage with CH 4 negatively correlated, but it has to be noted that not only the intensity of tillage influenced effluxes, but also climatic conditions played a huge role in determining the direction of effluxes. Conservation tillage is climate smart and, in this case NT at 120 kg N ha −1 , can be recommended because it sustained less effluxes especially during summer.