Historical Potato Yield Responses to Precipitation Indicate Supplemental Irrigation Not Profitable in Most Seasons in a Humid Temperate Climate

Climate change has created a growing interest in supplemental irrigation (SI) for consistent potato production in temperate humid regions. Knowledge about the influences of SI on potato productivity and profitability of SI and their annual variations are important for making decisions about SI adoption. However, there is a lack of long-term experimental data required to produce this knowledge. This study was conducted to understand the influences of SI on potato productivity and profitability using historical yield and weather data in Prince Edward Island (PEI), Canada. The 2000–2020 (excluding 2018) yields of Russet Burbank (RB), Shepody, Kennebec and Goldrush cultivars were conceptualized as the results of a long-term un-replicated experiment with growing season (GS) precipitation representing irrigation water supply treatments. Yield responses to GS precipitation followed second-order polynomial regressions with GS precipitation explaining 69%, 65%, 29% and 50% of yield variation for the four cultivars, respectively. Three of the 20 seasons received insufficient precipitation and would require SI; five received excessive precipitation and would benefit from soil dewatering; 12 received precipitation in the range of 280–400 mm, in which potato yields responded insensitively to water supply variation or SI created little yield response. These results indicate that consistent potato production requires both SI and soil dewatering. SI would generate net revenue in an extremely dry season, and in a very dry season for large field sizes, but not produce net revenue in most seasons regardless of field size. The annual variation and unpredictability in SI requirements and unprofitability of SI in most seasons present a great financial challenge for widely implementing SI in this traditionally rain-fed production region. Given that SI is only profitable in a very dry season with unpredictable occurrence, SI can be treated as insurance in fields with promising financial potential