For many crops, nitrogen use increases have been accompanied by well-recorded yield increases — at rates that show nitrogen's benefit, and also suggest that farmers may be becoming more agronomically nitrogen-efficient, requiring less nitrogen per unit of production. 

"In the absence of good information, we could do the wrong thing,” says Tom Tomich, co-author of the article and director of the Agricultural Sustainability Institute at UC Davis.

"Regulation without supporting data could fail to address the heart of the problem, or could damage agriculture,” says Tomich, who is also professor in the Department of Environmental Science and Policy at UC Davis, W.K. Kellogg Endowed Chair in Sustainable Food Systems and director of Sustainable Agriculture Research and Education Program. "Better information on nitrogen use is indispensable to collaborative development of effective solutions that can increase nitrogen use efficiency and save farmers money.”

The article makes recommendations on how data could be better compiled to improve our understanding of statewide trends in fertilizer use.    

This article is part of an ongoing study, The California Nitrogen Assessment (CNA), a project of the Agricultural Sustainability Institute at UC Davis and UC Sustainable Agriculture Research and Education Program. The CNA reviews existing data on nitrogen to draw connections between nitrogen use, surplus, and established environmental and human health effects of excess nitrogen. The CNA is a stakeholder-driven assessment that seeks public input on its research and products. To learn more about the California Nitrogen Assessment, visit

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