Ag's Contribution to California Smog Questioned

Several inconsistencies undermine the conclusion that agriculture is a dominant source of nitrogen oxides.

Published online: Sep 12, 2018 Articles
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Source: International Plant Nutrition Institute

A paper published January 2018 in Science Advances reported that losses from cropland of the smog-forming gases known as NOx contribute 20 to 32 percent of the state of California’s total emissions. A team led by the International Plant Nutrition Institute (IPNI), however, has published a technical comment (released on Sept. 12) questioning the findings. 

The comment, outlining several inconsistencies, suggests that agricultural emissions are considerably lower. It argues that the findings are undermined by the lack of agreement between modeled estimates and previous field measurements, the inappropriate extrapolation of field measurements taken during high emission periods, and the overestimation of nitrogen fertilizer consumption in California. The published comment calls for increased transparency in the assessment of nitrogen loss pathways, to support responsible management of crop nutrients in agriculture.