To compare and contrast changes in soil N cycling on decadal time scales and to learn more about sustainability of historic management regimes, N cycles were constructed for maize grown by indigenous Americans in Southern bottomlands from as early as 1200 to 500 years BP and for antebellum cotton on uplands. Although a range of N cycling exists in this historico-ecosystem analysis, both agroecosystems tend toward depletion of plant-available N.