Figure. Nitrogen budget aggregated from the eight crops in the U.S. from 1970 to 2019. N inputs include manure (Nman), atmospheric deposition (Ndep), fertilizer (Nfer), and biological N fixation (Nfix), and N output includes crop recovered N (Nrec). The time series of nitrogen surplus (Nspl) is shown by the red curve. The dashed line is the long-term average (1970–2019) N surplus.
The datasets include county-level total nitrogen input rates, nitrogen use efficiency(NUE), crop recovered N, N surplus, and planting area of eight crop types, including barley, corn, cotton, durum wheat, rice, sorghum, spring wheat, and winter wheat, in the U.S.from 1970 to 2019. More details can be found in Zhang et al., 2021, Global Biogeochemical Cycles. Eight data files are corresponding to the eight crop types. Each file has six columns:
“YEAR”: Year of the data
“State”: Name of the state
“crop_type”: Crop type
“County”: Name of the county
Area: Planting area, million hectors (Mha)
“Ninput”:Total nitrogen input rate, unit in kg N ha-1yr-1
“NUE”: Nitrogen use efficiency, unit in kg N kg-1N
“Recovered N”: Crop recovered nitrogen, unit in kg N ha-1yr-1
“Nsurplus”:Nitrogen surplus, unit in kg N ha-1yr-1
Citation: Zhang, J., Cao, P. and Lu, C., 2021. Half‐century history of crop nitrogen budget in the conterminous united states: variations over time, space and crop types. Global Biogeochemical Cycles, 35(10), p.e2020GB006876. https://doi.org/10.1029/2020GB006876
Decadal average nitrogen use efficiency (NUE) (a-e, unit in kg N kg−1 N yr−1) and N surplus (f–j, unit in Gg N yr−1) of corn in each county of the contiguous U.S. Annual planting area in each county has been used to calculate the county-level N surplus.