The Effects of Reduced Late-Season Irrigation on Potato, and How Evapotranspiration Differs Across Varieties

Monday, July 26, 2021
4:45 PM - 5:00 PM


Improving tuber quality using season-long and transitory deficit irrigation has been investigated for the past six decades. However, the effects of late-season deficit irrigation on tuber quality are poorly understood. This study was conducted to determine whether reduced late-season irrigation improves tuber quality while maintaining yield and investigates evapotranspiration (ET) differences of Alturas, Clearwater Russet (R.), Ranger R., R. Burbank, and Umatilla R. The effects of reduced late-season irrigation and ET measurements were investigated from 2018-2020 at the WSU-Othello research farm. Based on modeled ET, irrigation levels (IL), 40%, 60%, 80%, 100%, and 120% ET, were implemented at approximately 1500 day-degrees, about 110 days after planting. This time was chosen to investigate if reducing irrigation below the crop’s ET once the canopy and roots fully developed could be done without reducing yield. Crop ET was measured using environmental and soil sensors and the soil water balance method. Total yield was reduced on all the cultivars when reducing late-season irrigation below 100% ET. Grower return was maximized for four cultivars when replacing late-season irrigation with 100% ET; however, Alturas’ grower return was maximized with 80% ET. A significant positive relationship was found between the IL and growth crack incidence in Alturas. For all cultivars, a significant negative relationship was found between the IL and tuber specific gravity. Significant improvements in tuber fry color were achieved by reducing late-season irrigation below 100% ET, enabling tubers to be stored longer at colder temperatures. Lastly, the five cultivars shared similar ET up to full canopy cover, where two groups emerge. The ET of Alturas, Clearwater R., and Ranger R. was significantly higher than the other two cultivars. These findings provide growers with storage and production options and incentives to reduce water consumption while maximizing profits from higher quality tubers.

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