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

Authors: Paff, Kirsten; Fleisher, David; Timlin, Dennis

Submitted to: Computers and Electronics in Agriculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/12/2022
Publication Date: 4/15/2022
Citation: Paff, K.E., Fleisher, D.H., Timlin, D.J. 2022. Changes in the effects of water and nitrogen management for potato under current and future climate conditions in the U.S. Computers and Electronics in Agriculture. 197:106980. https://doi.org/10.1016/j.compag.2022.106980.
DOI: https://doi.org/10.1016/j.compag.2022.106980

Interpretive Summary: Washington State is a major potato producer and claims some of the highest potato yields in the world. Most of the potato crop is grown in sandy soils that drain very quickly and require high rates of nitrogen (N) fertilizer. This poses a high risk of N leaching, groundwater contamination and lost investment for the farmers. Temperatures in the Pacific Northwest are also expected to increase, which would directly impact the potato crop and potentially limit available irrigation water. Therefore, management guidelines are needed to help optimize agricultural water and N use. SPUDSIM is a mathematical potato model developed by USDA ARS that was used for this project. The model's ability to simulate the effects of varying levels of N fertilizer and irrigation on yields and N dynamics was demonstrated by comparing simulated results with experimental data from multiple years. The model was then run for multiple years of historic and generated future weather data. Historically, the best irrigation and water use efficiencies occurred with low irrigation and high N application. This management option also had the lowest N leaching loss. In contrast, high irrigation and low N application increased nutrient use efficiency. The highest yields were achieved using a high irrigation, high N application. Similar trends occurred under future climates, except higher nutrient use efficiencies occurred with lower irrigation and N use. In the future, N application appeared more important than irrigation amount for achieving the highest yields. The difference in yields between the most resource efficient and highest yielding treatments also decreased under future climate scenarios. These results benefit farmers and crop consultants in the potato industry in terms of optimizing their management options as well as promoting environmental stewardship.

Technical Abstract: 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 USDA-ARS 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. Maximum yields increased under RCP 4.5 as compared with historical values, though the yield increase was smaller for later years. Maximum yields increased initially for RCP 8.5 but decreased in later years. Water use was maximized 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 maximized 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.