<b>Data from: Water quality of an integrated crop–livestock system in the northern Great Plains</b>

Integrated crop-livestock (ICL) systems can potentially increase agricultural productivity in an environmentally sustainable manner. Impacts of ICL systems on water quality, however, have not been adequately studied. Rainfall simulations were used to examine effects of cropland and grass pasture vegetation types on surface runoff and water infiltrating into soil in a long-term ICL study near Mandan, ND USA. Simulations were conducted before and after grazing over a two-year period (August 2017 – May 2019). Water quality parameters included nitrate-N, nitrite-N, ammonia-N, phosphate-P, and total suspended solid (TSS) concentrations and loads in surface and infiltration waters. Water N and P compounds were determined using an AQ1 Discrete Analyzer, while TSS concentrations were determined by mass difference after passing a known sample volume through filter paper and drying to a constant mass. Surface runoff loads for N and P compounds were calculated by the sum of sample concentrations multiplied by sample volumes for all samples collected during each simulation event. As a supplement to water quality parameters, plant biomass and litter samples were collected, and percent cover of living vegetation, vegetation litter, and bare ground were estimated within a representative area of the sample site. Data may be used to understand ICL system impacts on water quality and are generally applicable to cropland and rangeland under a semiarid continental climate for the following soil types: Grassna, Linton, Mandan, Temvik, Williams, and Wilton.