Effects of Below Ground Controlled Injections of CO2 on Microbial Respiration of Soil Planted With Wheat (Triticum aestivum L.)

 Below-ground carbon dioxide (CO2) emissions occur naturally at CO2 springs, but the risk of occurrence at other sites will increase as geologic CO2 storage is implemented to help mitigate climate change. This investigation examines the effect of controlled injection of below ground CO2 emission on wheat plant and soil microbial respiration where spring wheat (triticum aestivum L.) was grown. The study involved setting up eight (8) experimental plots (each 2.5 x 2.5m) for the growth of spring wheat. The experimental plots labelled A1 - A8 (A1, A6 and A7 were gassed plots while A2, A3, A4, A5 and A8 were used as control plots). Soil CO2 concentration was increased by the release of 
concentrated CO2 gas from a source point 60 cm below the soil for eight (8) weeks at the rate of 1L-1 via tubes into the soil when wheat was grown. Five plots were used as control, while three plots were used as treatment plots with a regulated meter gas supply. The variability of CO2 concentrations was determined by a revised 2D method known as Barholing using a geotechnical Instruments GA2000 gas analyser to map CO2 at 30 cm depth across each plots. This was used to measure the dispersion of CO2 throughout the plots. This method which produced contour plots of spatial variation shows the rate of dispersion of soil gas in the treated plots. The concentrations of CO2 at the centre of the plots were different, showing values up to 70% CO2 but reduced rapidly from the centre to plot borders. No significant changes in microbial biomass or carbon utilisation were observed (at P>0.05), but a trend towards reduced microbial respiration was apparent in the gassed plots.