Impact of changing land use practices on nitrate export by the Mississippi River

摘要: [1] The increased use of nitrogen fertilizer in the Mississippi River Basin since 1950s has been blamed for declining water quality, degradation aquatic ecosystems and growth a seasonal hypoxic zone Gulf Mexico. In this study, we IBIS terrestrial ecosystem model HYDRA transport to examine how agricultural practices climate influenced cycling across nitrate export Gulf. The modeling system accurately depicts observed trends interannual variability by (r2 > 0.83), several major tributaries, between 1960 1994. challenge simulating from central western sub-basins highlights key role processes like denitrification. simulations demonstrate that three factors led doubling 1960: (1) an increase application rates, particularly on maize; (2) runoff basin; (3) expansion soybean cultivation. By early 1990s, fertilized crops may have accounted almost 90% leached river system, despite representing only 20% watershed area. majority exported appears originate “hot spots,” including stretch “Corn Belt” Iowa, Illinois, Indiana. relative contribution such heavily lands, those close proximity higher order streams, can be even greater during wet years.