Journal ArticleHalf‐Century History of Crop Nitrogen Budget in the Conterminous United States: Variations Over Time, Space and Crop TypesZhang, Jien; Cao, Peiyu; Lu, Chaoqun2021-10-0110324600Global Biogeochemical Cycles35100886-6236https://doi.org/10.1029/2020GB0068761945036; 1903722National Science Foundation