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Nelson Mandela University (2021)

Quantifying variability of emissions of greenhouse gas (CO2& CH4) across selected soils and agricultural practices

Sebake, Tebogo Matsimela

Titre : Quantifying variability of emissions of greenhouse gas (CO2& CH4) across selected soils and agricultural practices

Auteur : Sebake, Tebogo Matsimela

Université de soutenance : Nelson Mandela University

Grade : Master of Science (MS) 2021

Résumé partiel
Increasing concentrations of greenhouse gases (GHG’s)in the atmosphere are warming the planet, and agriculture is responsible for about 30% of these emissions. Soils act as a host for greenhouse gases, since both their storage and emission capacities are large, accounting for two-times the amount of carbon in the atmosphere and in plant and animal life. It sequesters large amounts of carbon, and because agricultural practices depend on soil for production, the practices influence the soil’s ability to store the carbon effectively. Production soils emit greenhouse gas, predominantly carbon dioxide and methane, which are assessed for emissions in this study. Climate change creates unpredictability in precipitation and temperature ; farmers need to be flexible and adapt production methods to such environmental changes in order to continue producing sustainably. Global food production needs to grow drastically to meet the projected demands for rising population and diet shifts ; studies have shown that feeding a more populated and a more affluent, equal, world will require roughly a doubling of agricultural production by 2050, which means more GHG emissions from the soil. To enable better control on these emissions, their links to agricultural practices need to be better quantified. The study was done in two areas : (1) long-term comparative farming systems research trial with controlled vegetable plots, in the agricultural school of Nelson Mandela University, in George, Western Cape province and (2) long-term wheat research trial of the Free State University, in Bethlehem, Free State province. The objective in study area one is to assess and compare GHG emissions from conventional and organic systems. Temperature and soil moisture were measured during gas samples to establish the influence they have on gas emissions. The objective in study area two is to assess and compare GHG emissions from no-till, plough, and stubble mulch. Stubble mulch refers to crop residue left in place on the land as a surface cover during fallow periods. Two polypropylene canisters are placed in a sampled plot to trap gas emitted from the soil. Analyses of the trapped gases in the headspace gives concentrations of CO2and CH4that was emitted during the duration the canister was closed.

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Page publiée le 12 janvier 2023