Capacity for bioreactors and riparian rehabilitation to enhance nitrate attenuation in agricultural streams

•Combing edge-of-field N-removal tools attenuated nitrate across riparian buffers.•Hydrologic variability drove nitrate fluxes and the performance of attenuation tools.•Farm-scale N-loss reductions were small compared to groundwater N legacies. Globally, small agricultural waterways fed by springs, tile drains, and seeps can disproportionately contribute to downstream nutrient loading, which is associated with declines in water quality and ecosystem functions. Treating nitrate using a multiple tool, multiple-scale approach in small waterways could offer improved management of these sources. We used a before-after-control-impact design to test the suitability of three small (