Extreme climate increased crop nitrogen surplus in the United States

Abstract

Increasing extreme climate conditions present significant threats to crop nitrogen (N) management and environmental conservation in the United States. Previous studies have examined the impacts of extreme climate on crop production but often overlooked its impacts on N loss from agricultural areas to the environment. Here we examined the relationship between county-level N surplus (the part of N that is not recovered by crops) and extreme climate conditions for corn in the U.S. during 1981–2016. We adopted multi-source long-term datasets of corn N budget and growing season (defined from May to August) maximum temperature and precipitation for each corn-planting county. Compared with the long-term N surplus trend, we found an increase of 51% and 47% in corn N surplus associated with extremely high temperature and extremely low precipitations, respectively. A moderate N surplus increase (20%) was associated with extremely high precipitations, while an N surplus decrease of 14% was shown to be related to extremely low temperatures. Across the U.S., the Midwest and the Northern Great Plains were identified as N surplus hotspots when extreme climate conditions occur. As the major corn-planting region, the Midwest accounted for 35% of the national extreme county-year samples but yielded 68% of the national total N surplus associated with extreme climate conditions. Our results highlighted the urgency of understanding the impacts of extreme climate conditions on crop nutrient losses and identifying the effective intervention practices to adapt to more frequent climate extremes in the future.