Grasses and Gases: Modeling Human Dynamics of Lawn Fertilization and Resultant Nitrous Oxide Emissions

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Nitrous oxide is released into the atmosphere from a variety of human activities. This gas is roughly 300 times as potent as carbon dioxide in trapping heat in the Earth?s atmosphere, and thus even small quantities of emissions may constitute a meaningful share of US greenhouse gas emissions. One path for nitrous oxide releases is from the application of fertilizers to lawns because a portion of these fertilizers is converted to nitrous oxide by soil bacteria. Not only are the physical factors that affect nitrous oxide emissions from households not well quantified, but social science research and research into climate change mitigation laws and policies associated with lawncare has not been a focus in the past. An integrated, interdisciplinary study is needed to answer questions related to (1) the physical processes that lead to nitrous oxide emissions from household nitrogen-containing fertilizer use, (2) the types and levels of individual and household activities that affect household nitrous oxide emissions from fertilizer use; (3) the values, beliefs and norms associated with these individual and household activities; and (4) the communities and social networks associated with these activities. This project is a study of the Richland Creek Watershed, which encompasses 28.5 square miles of primarily residential neighborhoods in Nashville, Tennessee. These neighborhoods represent a diverse range of residents in terms of race, income, education, and ownership patterns. A coordinated set of biophysical and social-science data will be collected and analyzed to address the science questions. To understand how social and economic influences affect fertilizer use in Richland Creek neighborhoods, the research team will conduct a series of surveys with 600 households grouped in 60 blocks in the watershed. We also will conduct 60 focus groups, one for each sampled block. To provide the link to the release of nitrous oxide, physical samples will be taken at locations around the watershed. Nitrous oxide fluxes from the soil will be measured using soil covers and soil moisture and temperature will be measured at the sampling sites using a wireless sensor array.Using data derived in this research, theoretical explanations of household, sub-neighborhood, and neighborhood behaviors and their effect upon fertilization rates will be tested and, through links with measured biophysical processes, emission rates of a powerful greenhouse gas, nitrous oxide, will be included. The project will lead to knowledge of how much of nitrogen-containing fertilizer applied to lawns is converted to nitrous oxide as affected by soil and meteorological conditions; how household lawncare decisions around fertilizer use are affected by a neighborhoods? norms and characteristics; which household-level beliefs, norms, and characteristics affect fertilizer use; how neighborhood-level norms and characteristics interact with household characteristics; and how the combined knowledge of emissions and behavioral characteristics can be used to explore options to effect reductions of nitrous oxide emissions from fertilizer use. In particular, the research results may indicate that a number of policy or community-level interventions may be appropriate for reducing the household share of greenhouse gas emissions and that these interventions may be quite cost effective in comparison with more often used regulatory measures targeting industrial sources.