Historical nitrogen fertilizer use in agricultural ecosystems of the contiguous United States during 1850–2015: application rate, timing, and fertilizer types

Abstract

Abstract.A tremendous amount of anthropogenic nitrogen (N) fertilizer has been applied to agricultural lands to promote crop production in the US since the 1850s. However, inappropriate N management practices have caused numerous ecological and environmental problems which are difficult to quantify due to the paucity of spatially explicit time-series fertilizer use maps. Understanding and assessing N fertilizer management history could provide important implications for enhancing N use efficiency and reducing N loss. In this study, we therefore developed long-term gridded maps to depict crop-specific N fertilizer use rates, application timing, and the fractions of ammonium N (NH Geospatial analysis revealed that hotspots for N fertilizer use have shifted from the southeastern and eastern US to the Midwest, the Great Plains, and the Northwest over the past century. Specifically, corn in the "Corn Belt" region received the most intensive N input in spring, followed by the application of a large amount of N in fall, implying a high N loss risk in this region. Moreover, spatial-temporal fraction of NH + 4 -N and NO − 3 -N varied largely among regions. Generally, farmers have increasingly favored ammonia N fertilizers over nitrate 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 N addition impacts, and improve N management to alleviate environmental problems. Datasets used in this study are available at https://doi.org/10.1594/PANGAEA.883585.

Are We Getting Better in Using Nitrogen?: Variations in Nitrogen Use Efficiency of Two Cereal Crops Across the United States

“…We obtained historical state-level crop yield data, from the USDA National Agricultural Statistics Service (NASS; http://www.nass.usda.gov/index.asp) crop databases, and state-level annual N-fertilizer use data developed by a recent study (Cao et al, 2018). Other anthropogenic N sources considered in this study include manure N application and atmospheric N deposition for the two crops, and residual N from previous-year soybean fixation for corn only.…”

“…N Fertilizer Use N fertilizer consumption of these two crops accounts for more than 50% of national total N fertilizer use in the United States (USDA-ERS, 2013). Details of the development of N fertilizer use rates and gap-filling are described in Cao et al (2018). The survey records cover approximately 90% of national corn and winter wheat planting area (Table S1).…”

“…A recent study in China also found that N uptake first decreased and then plateaued with grain yield improvement (Meng et al, 2016). During the period of 1970 to 2015, ammonium-N is the dominant fertilizer type across the United States (Cao et al, 2018), which has a high potential for volatilization loss and leaching loss after being nitrified. However, it remains untested whether these enhanced efficiency fertilizers can sustain a long-term corn yield increase.…”

“…However, winter wheat yield only explains~8% of interannual variations in N surplus (Figure 3f). First, the majority of N fertilizer is applied to both cropping systems before planting in the United States, with March-April for corn and August to September for winter wheat (Cao et al, 2018). We ascribed the different drivers of N surplus between corn and winter wheat to the following reasons.…”

“…According to a few existing studies, N fertilizer application rate varied among subregions within a single nation, which is likely the results of differences in the physical environment and the state-oriented policy (Bierman et al, 2012;Cao et al, 2018). According to a few existing studies, N fertilizer application rate varied among subregions within a single nation, which is likely the results of differences in the physical environment and the state-oriented policy (Bierman et al, 2012;Cao et al, 2018).…”