Changes in the effects of water and nitrogen management for potato under current and future climate conditions in the U.S

A major portion of the United States' potato (Solanum tuberosum, L.) production occurs in the state of Washington. Local intensive management practices involving heavy nitrogen and irrigation use can result in substantial resource loss due to sandy soils. It is important to examine the effects of nitrogen and water management practices under current climate conditions and how these effects may change in the future to develop best management practices. This study simulated the response of the Ranger Russet variety at two locations to three nitrogen (N) (168, 336, and 504 kg N/ha) and four irrigation (475, 645, 748, and 816 mm) rates using the USDAARS SPUDSIM potato model. The model was calibrated and evaluated using field data. Future weather was generated for two Representative Concentration Pathways (RCPs) (4.5 and 8.5) and four years (2030, 2050, 2070, and 2095). Management practices were evaluated based on whether yield, N, or water use was the priority. The highest yields were achieved when the highest input levels were used across all climate scenarios, but irrigation levels had minimal effect on yields for RCP 8.5 2070 and 2095. High input yields increased under RCP 4.5 as compared with historical values, though the yield increase was smaller for later years. High input yields increased initially for RCP 8.5 but decreased in later years. Water use was most efficient under low irrigation/ high N treatments. N leaching decreased by as much as 83% for low irrigation/high N treatments, as compared to high irrigation/high N, though this also resulted in <= 23% yield reductions; however, this yield reduction decreased with increasing RCP and year. Nitrogen use efficiency was highest under high irrigation/low N conditions historically, and under low irrigation/low N in the future. More resource efficient management practices resulted in yield reductions, but the differences in yield between the most efficient practices and the highest yielding practices decreased as climate change became more severe. These results benefit growers by evaluating management options based on different goals and promoting environmental stewardship.