Farms, fertilizers and smog

Residents of California’s Central Valley, and particularly its farmers, got some bad news recently. In late January, a study done by UC Davis scientists and published in the journal Science Advances reported that farm soils fertilized with nitrogen are the source of about 40 percent of the nitrogen oxides emissions in California.

Nitrogen oxides (NOx) are the main ingredient in smog and contribute to damaging health effects, such as heart disease, asthma and other respiratory issues. According to a UC Davis article written by Kat Kerlin, the World Health Organization estimates air pollution causes one in eight deaths worldwide.

Fifty years ago, NOx affected mostly urban areas with lots of cars, such as Los Angeles. The advent of catalytic converters dramatically reduced smog levels there, and today the worst air pollution is found in rural areas such as the Central Valley, and particularly in its poorest communities.

“Since this source of NOx can remain local, largely in rural farming communities, we need to develop a kind of ‘catalytic converter’ for soils and farms,” senior author Ben Houlton, a professor with the UC Davis Department of Land, Air and Water Resources, told Kerlin.

Studies have shown that current fertilizing methods are inefficient and leave as much as half of the nitrogen in the soil, from which it is released as NOx. As the UC Davis study suggests, however, there are a number of practical steps growers can take to make nitrogen uptake more efficient, such as using slow-release fertilizers; fostering healthy soils that restore carbon; and the use of precision agricultural practices, particularly in perennial crops such as almonds.

We encourage local agriculturalists to commit themselves to lowering NOx levels by working with agricultural scientists to improve fertilizer management. The alternative is to wait until the government steps in to mandate pollution reductions, and nobody wants that to happen.