A recent study by the University of California – Davis says farm fields are causing major nitrogen oxide pollutionin the state. The study indicates that between 20 and 32 percent of that smog is caused by farm fields with fertilizer applications.

The study says recent findings show that agriculture is one of the dominant sources of nitrogen oxide in the U.S. It says the impact is especially large in the Midwest, where fertilizer inputs are substantial.

The study took place in California’s central valley, with the authors saying more study is needed around the state before new policies are suggested.If the study is proven, it means a lot of new regulations for farms around the state, with producers and agriculture industry stakeholders not happy about the idea.

Renee Pinel of the Western Plant Health Association says it’s just one study that hasn’t even been peer-reviewed yet. A wide range of universities and regulatory agencies have studied this and not found agriculture to be a significant contributor of nitrogen oxide.