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

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. The gas is analysed by a G2201-i Picarro gas analyser, presently the only such instrument in South Africa. The analyser’s near-infrared Cavity Ring Down Spectroscopy technology is capable of simultaneous measurements of CO2and CH4down to parts per million. In study area one, conventional plots (R2T6 & R1T6) emitted 65.089ppm CO2and 61.159ppm CO2, and 0.0010ppm CH4and 0.0004ppm CH4, respectively. Organic plots (R1T3 & R2T3) emitted 53.264ppm CO2and 47.885ppm CO2, and 0.0023ppm CH4and 0.0019ppm CH4respectively. Thus, conventional plots emitted 19.98% & 30.98% more CO2than organic plots; but organic plots emitted 81.97% & 155.5% more CH4thanconventional plots. In study area two, ploughed soils emitted 38.727ppm CO2and 0.015ppm CH4, no-tilled soils emitted 31.798ppm CO2 and 0.011ppm CH4andstubble mulched soils emitted 28.373ppm CO2 and 0.009ppm CH4. Thus, ploughed soils emitted 19.65%more CO2than no-tilled soils, no-tilled soils emitted 11.38% more CO2 than stubble mulched soils and ploughed soils emitted 30.36% more CO2 than stubble mulched soils. Ploughed soils emitted 30.77% more CH4 than no-tilled soils, no-tilled soils emitted 20% more CH4 than stubble mulched soils and ploughed soils emitted 50% more CH4than stubble mulched soils. Moist soils result in decreased CO2emissions in conventional plots and increased CH4emissions in organic plots. Increasing temperature patterns are followed by a trend of increasing gas emissions. Reducing GHG emissions from agriculture and developing sustainable tillage practices can help mitigate climate change and increases the chances of stabilizing GHG concentrations and temperature control within a required range.Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 202

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

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. The gas is analysed by a G2201-i Picarro gas analyser, presently the only such instrument in South Africa. The analyser’s near-infrared Cavity Ring Down Spectroscopy technology is capable of simultaneous measurements of CO2and CH4down to parts per million. In study area one, conventional plots (R2T6 & R1T6) emitted 65.089ppm CO2and 61.159ppm CO2, and 0.0010ppm CH4and 0.0004ppm CH4, respectively. Organic plots (R1T3 & R2T3) emitted 53.264ppm CO2and 47.885ppm CO2, and 0.0023ppm CH4and 0.0019ppm CH4respectively. Thus, conventional plots emitted 19.98% & 30.98% more CO2than organic plots; but organic plots emitted 81.97% & 155.5% more CH4thanconventional plots. In study area two, ploughed soils emitted 38.727ppm CO2and 0.015ppm CH4, no-tilled soils emitted 31.798ppm CO2 and 0.011ppm CH4andstubble mulched soils emitted 28.373ppm CO2 and 0.009ppm CH4. Thus, ploughed soils emitted 19.65%more CO2than no-tilled soils, no-tilled soils emitted 11.38% more CO2 than stubble mulched soils and ploughed soils emitted 30.36% more CO2 than stubble mulched soils. Ploughed soils emitted 30.77% more CH4 than no-tilled soils, no-tilled soils emitted 20% more CH4 than stubble mulched soils and ploughed soils emitted 50% more CH4than stubble mulched soils. Moist soils result in decreased CO2emissions in conventional plots and increased CH4emissions in organic plots. Increasing temperature patterns are followed by a trend of increasing gas emissions. Reducing GHG emissions from agriculture and developing sustainable tillage practices can help mitigate climate change and increases the chances of stabilizing GHG concentrations and temperature control within a required range.Thesis (MSc) -- Faculty of Science, School of Environmental Sciences, 202

Earth Stewardship Science—Transdisciplinary Contributions to Quantifying Natural and Cultural Heritage of Southernmost Africa

Evaluating anthropogenic changes to natural systems demand greater quantification through innovative transdisciplinary research focused on adaptation and mitigation across a wide range of thematic sciences. Southernmost Africa is a unique field laboratory to conduct such research linked to earth stewardship, with ‘earth’ as in our Commons. One main focus of the AEON’s Earth Stewardship Science Research Institute (ESSRI) is to quantify the region’s natural and cultural heritage at various scales across land and its flanking oceans, as well as its time-scales ranging from the early Phanerozoic (some 540 million years) to the evolution of the Anthropocene (changes) following the emergence of the first human-culture on the planet some 200 thousand years ago. Here we illustrate the value of this linked research through a number of examples, including: (i) geological field mapping with the aid of drone, satellite and geophysical methods, and geochemical fingerprinting; (ii) regional ground and surface water interaction studies; (iii) monitoring soil erosion, mine tailing dam stability and farming practices linked to food security and development; (iv) ecosystem services through specific biodiversity changes based on spatial logging of marine (oysters and whales) and terrestrial (termites, frogs and monkeys) animals. We find that the history of this margin is highly episodic and complex by, for example, the successful application of ambient noise and groundwater monitoring to assess human-impacted ecosystems. This is also being explored with local Khoisan representatives and rural communities through Citizen Science. Our goal is to publicly share and disseminate the scientific and cultural data, through initiatives like the Africa Alive Corridor 10: ‘Homo Sapiens’ that embraces storytelling along the entire southern coast. It is envisioned that this approach will begin to develop the requisite integrated technological and societal practices that can contribute toward the needs of an ever-evolving and changing global ‘village’