New Study Highlights Importance of Agricultural NOx Pollution

Urban air pollution grabs headlines in California news. Air pollution often brings to mind cars stuck in the congested streets of Los Angeles or the Bay Area. However, new research led by Maya Almaraz, a postdoc from the University of California, Davis brings rural air pollution to light.

Specifically, the study looks at agriculture as a source of nitrogen oxide (NOx) pollution, one of the primary contributors to unhealthy air quality in the Central Valley. The study found that NOx from agricultural soils are a previously unrecognized contributor of California’s NOx pollution. Almaraz and her team estimate that agricultural soils contribute between 20% and 51% of the state’s total NOx emissions. The study used two primary methods to determine NOx emissions: a “bottom-up” approach using spatial modeling and a “top-down” tactic that made airborne measurements.

This significant source of NOx pollution was undiscovered because of gaping flaws in previous methodologies. The last time empirical measurements were taken of the San Joaquin Valley was 20 years ago. Since then, the California Air Resource Board has extrapolated California NOx emissions primarily from farms within 200 miles from Sacramento. This neglects heavily fertilized agricultural soils elsewhere in the state.

The study offers a handful of solutions to reduce soil emissions, among them is to increase fertilizer efficiency. Other options include cultivating cover crops that can absorb residual nitrogen or precision fertilization instead of broadcasting. Using fertilizer efficiently can not only saves money for farmers but also prevents some of the $210 billion in environmental and health damages caused by agricultural nitrogen losses nationwide.

This new look at air pollution sources, especially in the Central Valley, will require innovative approaches. However, as we have seen with the Climate Smart Agriculture programs throughout the state, California farmers can and will embrace innovation.

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