In California, a University of California, Davis study found that a previously unrecognized source of nitrogen oxide is contributing up to about 40% of the NOx emissions in California – Nox is a primary component of air pollution, is smog-forming, and contributes to heart disease, asthma and other respiratory issues. The study compared computer models with estimates collected from scientific flights over the San Joaquin Valley and both the model and flight data suggested that between 25% and 41% of NOx emissions comes from soils with heavy nitrogen fertilizer applications.
NOx gases are produced in oxygen-poor soils when microbes break apart nitrogen compounds in the fertilizer. The release of those gases from fertilized soils increases at high temperatures due to increased microbial activity.
Some of the state’s worst air quality problems are now in rural areas, particularly the Central Valley region, which is also one of the world’s most highly productive agricultural areas. Roughly half of the fruits and nuts produced in the United States are grown there. The study suggests potential solutions for reducing NOx soil emissions, primarily through different forms of fertilizer management.