Carbon Sequestration and Greenhouse Gas Emission Reduction from Horticultural Production Practices
Marble, Stephen Christopher
Type of Degreedissertation
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Over the past three decades, one issue which has received significant attention from the scientific community is climate change and the possible impacts on the global environment. Increased atmospheric carbon dioxide (CO2) concentration, along with other trace gases [i.e., methane (CH4) and nitrous oxide (N2O)] are widely believed to be the driving factors behind global warming. Much of the work on reducing greenhouse gas emissions (GHG) and carbon (C) sequestration has been conducted in row crop and forest systems; however, virtually no work has focused on contributions from sectors of the specialty crop industry such as ornamental horticulture. Ornamental horticulture is a large scale industry which impacts rural, suburban, and urban landscapes. While this industry may have negative impacts on the global environment (e.g., CO2 and trace gas efflux), it also has the potential to reduce greenhouse gas emissions and increase C sequestration by altering current production practices. The objective of this research was to develop baseline estimates of trace gas emission levels from current horticultural production practices and then examine ways in which these production practices can be altered to decrease emissions and increase C sequestration. To develop baseline estimates of trace gas emissions from container plant production, efflux patterns of CO2, CH4, and N2O associated with four different nursery container sizes [3.0 L (trade gal; TG), 3.8 L (#1; 1 gal), 7.6 L (#2; 2 gal), and 11.4 L (#3; 3 gal)] were determined using dwarf yaupon holly (Ilex vomitoria ‘Nana’ L.) grown under common production practices for one year. Weekly measurements indicated that CO2 and N2O fluxes were highest in the largest containers (#3). There was a significant positive relationship between container size and CO2 efflux. Nitrous oxide efflux followed a similar pattern, except there were no differences between the two smallest container sizes. Methane flux was consistently low and had no significant effect on total trace gas emissions. Results from this study begin to address uncertainties regarding the environmental impact of the horticulture industry on climate change while providing baseline data of trace gas emissions from container production systems needed to develop future mitigation strategies. In a second study, efflux patterns of CO2, CH4, and N2O associated with three different fertilization methods (dibble, incorporated, or topdressed) commonly used in nursery container production were determined. Results indicated that CO2 fluxes were slightly lower when fertilizer was dibbled compared to the other two methods. Nitrous oxide fluxes were consistently highest when fertilizer was incorporated. Methane flux was generally low with few differences among treatments. Results from this study begin to provide data which can be used to implement mitigation strategies in container plant production which will help growers adapt to possible emission regulations and benefit from future GHG mitigation or offset programs.