Characterizing potato yield responses to water supply in Atlantic Canada’s humid climate using historical yield and weather data: Implications for supplemental irrigation

Abstract

Knowledge about potato yield responses to water supply at low, optimum and high levels is required to inform supplemental irrigation (SI), but short-term irrigation experiments may not produce this knowledge in a humid environment because of the difficulty in accurately controlling water supply with uncertain precipitation. This study was conducted to characterize potato yield responses to water supply by treating the 2001–2018 potato yields in Prince Edward Island (PEI), Canada as the results of an un-replicated irrigation experiment with growing season (GS) precipitation as irrigation water supply and utilize the results to inform SI. Yield responses to GS precipitation followed a second-order polynomial regression, with 88% of yield variation being explained by GS precipitation. The yield increased from 19.2 to 33 Mg/ha as GS precipitation increased from 150 to 360 mm, responded relatively insensitively (33–35 Mg/ha) when GS precipitation was between 360 and 460 mm and decreased as the precipitation exceeded 460 mm. Water deficiency/excess calculated as the difference between GS precipitation and evapotranspiration of the potato plant (ETc) indicates that 16 of the 18 seasons required SI of 30–300 mm while four of the 18 seasons required soil dewatering of 30–100 mm to maximize potato yields. The yield regression equation predicted that SI using a center-pivot system could generate net profit in an extremely dry year, but it is unlikely to do so in most years. Depending on the year, SI could use anywhere between 2.6% and 23% of annual average recharge in an intensively potato-cropped watershed, which can impose high stress on the groundwater discharge-dependent ecosystems in a very dry season. This study demonstrates that long-term potato yield responses to precipitation in a humid climate can provide important information to inform SI management and water allocation.