Simulating weather effects on potato yield, nitrate leaching, and profit margin in the US Pacific Northwest

The US Pacific Northwest is one of the most productive potato regions in the world. However, due to the high inputs, nitrate contamination of groundwater is frequently documented, and maximizing crop productivity while minimizing nitrate leaching is still challenging. The goal of this study was to assess how irrigation level, soil type, and weather condition during various phenological phases would affect tuber yield and the associated nitrate leaching and profit margin. The Cropping System Model (CSM)-SUBSTOR-Potato was used to simulate the response variables for various scenarios that comprised two soil types, five irrigation levels, five phenological phases, five weather conditions, and 75 years of historical weather data for 3 locations in this region. The simulation results showed that nitrate leaching was higher with a higher amount of irrigation and for a lighter soil. Tuber yield and profit margins were lowest for a lighter soil and highest for 300 mm of irrigation for an extremely-drained soil and 400 mm of irrigation for a well-drained soil. The increase in profit margins with an increase in total irrigation up to 400 mm was highest for a well-drained soil, whereas the decrease in profit margins with an increase in irrigation beyond a total amount of 300 mm was larger for an extremely-drained soil. For the different types of weather scenarios that were studied, only severe hot weather had an impact on tuber yield and profit margins. The reduction was highest at tuber bulking and significant when hot weather continued from sprout development through tuber bulking or from plant establishment through tuber maturation. However, any change in weather condition from the long-term average for any growth phase did not affect leaching. These findings might be helpful to potato growers in this region to protect their potatoes from adverse weather conditions through appropriate mitigation strategies.