Historical Nitrogen Fertilizer Use in Agricultural Ecosystem of the
Continental United States during 1850–2015: Application rate,
Timing, and Fertilizer Types
Abstract. Tremendous amount of anthropogenic nitrogen (N) fertilizer has been applied to agricultural lands to promote the crop production in the United States since the 1850s. However, inappropriate N management practices caused numerous ecological and environmental problems which are difficult to quantify due to paucity of historically spatially explicit fertilizer use maps. Understanding and assessing N fertilizer management history could provide essential implications for enhancing N use efficiency (NUE) and reducing N loss. In this study, we therefore developed long-term gridded maps depicting crop-specific N fertilizer use rate, timing, and fraction of ammonium N (NH4+-N) and nitrate N (NO3−-N) across the contiguous U.S at a resolution of 5 km × 5 km during 1850–2015. We found that N use rates of the U.S. increased from 0.28 g N m−2 yr−1 in 1940 to 9.54 g N m−2 yr−1 in 2015. Geospatial analysis revealed that the hotspots of N fertilizer use have shifted from the southeastern and eastern U.S. to the Midwest and the Great Plains during the past century. Specifically, corn of the Corn Belt region received the most intensive N input in spring, followed by large N application amount in fall, implying a high N loss risk in this region. Moreover, spatial-temporal fraction of NH4+-N and NO3−-N varied largely among regions. Generally, farmers have increasingly favored NH4+-N form fertilizers over NO3−-N fertilizers since the 1940s. The N fertilizer use data developed in this study could serve as an essential input for modeling communities to fully assess the N addition impacts, and improve N management to alleviate environmental problems. Datasets available at https://doi.pangaea.de/10.1594/PANGAEA.883585.