Greenhouse gas emissions from different crop production and management practices in South Africa

Application of synthetic (N) fertiliser (such as urea) and incorporation of crop residues into soil result in nitrous oxide (N2O) emissions. Similarly, application of urea and lime to the soil results in carbon dioxide (CO2) emissions. Greenhouse gases (GHGs) emanating from application of synthetic fertiliser, lime and crop residues retained in the field after harvest during field crop production in South Africa were calculated in this study. The objective was to establish GHG profiles of the field crops in South Africa that can inform national mitigation plans that are currently lacking details regarding the agriculture sector. The calculations used Agriculture and Land Use National Greenhouse Gas Inventory Software which is based on the Intergovernmental Panel on Climate Change Guidelines for National GHG Inventory. GHG emissions were calculated and compared among different crop production and management practices. It is estimated that production of field crops resulted in a total of 5.2 million tonnes of CO2 equivalent (CO2-eq) emissions in South Africa in 2012. Application of synthetic fertiliser contributes the highest emissions with 57% of national total crop CO2-eq emissions, followed by addition of lime (30%) and crop residues retained in the field (13%). Production of cereal crops accounts for 68% of national total field crops' GHG emissions followed by other field crops (14%), legumes and oilseeds (11%) and vegetables (7%). Cultivations of maize, wheat and sugarcane result in highest commodity emissions. Highest GHGs per area planted were from the production of tomatoes with 1.65 t of CO2-eq ha−1. These results show that mitigation plans of emissions from field crops in South Africa need to focus more on sustainable improvement of soil fertility, optimum application of synthetic N fertiliser and crop residues.