/ Central Valley Content for 91¿´Æ¬ Davis en /climate/news/smog-forming-soils <p>A previously unrecognized source of nitrogen oxide is contributing up to about 40 percent of the NOx emissions in California, according to a study led by the 91¿´Æ¬, Davis. The study traces the emissions to fertilized soils in the Central Valley region.</p> January 31, 2018 - 12:26pm Katherine E Kerlin /climate/news/smog-forming-soils