Evaluating the effects of reduced late-season irrigation on fry color of five processing potato cultivars

Authors: Gonzalez-Tapia, Francisco - Paco; PAVEK, MARK - Washington State University; KNOWLES, RICHARD - Washington State University; HOLDEN, ZACHARY - Washington State University

Submitted to: Potato Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/13/2024
Publication Date: 5/25/2024
Citation: Gonzalez Tapia, F., Pavek, M.J., Knowles, R.N., Holden, Z. 2024. Evaluating the effects of reduced late-season irrigation on fry color of five processing potato cultivars. Potato Research. https://doi.org/10.1007/s12230-024-09948-4.
DOI: https://doi.org/10.1007/s12230-024-09948-4

Interpretive Summary: Water scarcity is an increasing challenge for agriculture, particularly for potato growers in regions where water resources are limited. Simultaneously, the frozen potato-processing industry has stringent quality requirements, especially concerning the color and lightness of the fries. This puts potato farmers in a difficult position: they need to figure out how to conserve water while still meeting the high-quality standards for fry color. To address this issue, a comprehensive multi-year study was carried out. The research focused on five different russet potato cultivars and experimented with five varying levels of late-season irrigation. The study found that reducing the amount of water used for irrigation late in the growing season by 20-40% led to significant improvements in fry color for four out of the five potato types examined. However, the study also revealed that reducing water usage by more than 40% or increasing it to 120% of the recommended level could result in darker, less desirable fries. Interestingly, the benefits or drawbacks were also influenced by the storage temperature of the potatoes before frying. The findings of this study offer nuanced, practical insights for potato growers. By adhering to these new irrigation guidelines, farmers can optimize water usage and improve the quality of fries they produce, thereby meeting the strict requirements of the frozen potato-processing industry. This research serves as a valuable roadmap for growers, enabling them to make more informed decisions about irrigation while considering the type of potato and storage conditions. The end result is a more sustainable approach to potato farming that benefits both the environment through water conservation and the economy by producing a higher-quality product.

Technical Abstract: In light of escalating water scarcity challenges and stringent quality standards set by the frozen potato-processing industry, this multi-year study aimed to assess the potential for enhancing tuber fry color through reduced late-season irrigation, while also minimizing water usage. The experimental design included five different irrigation levels, determined by modeled evapotranspiration, and involved five russet potato cultivars. Irrigation commenced between 95 and 110 days after planting, a period that coincided with approximately 1500 cumulative day degrees and peak development of canopy cover and root systems. Irrigation was halted at the point of vine kill, which occurred around 150 to 155 days post-planting. Tubers were subsequently evaluated for fry color lightness after being stored for 45 and 90 days at three different temperatures: 4.4°C, 6.7°C, and 8.9°C. Fry color was quantified using a photovolt reflectometer to measure percent light reflectance, with higher values indicating lighter-colored fries. The study found that a reduction in late-season irrigation by 20-40% led to significant improvements in fry color for four out of the five tested cultivars. However, no noticeable improvement in fry color was observed for the Ranger Russet cultivar following reduced late-season irrigation. When late-season irrigation was reduced by more than 40%, Clearwater Russet, Russet Burbank, and Umatilla Russet cultivars produced fries with darker colors when stored at 4.4°C and 6.7°C. Moreover, excessive irrigation (120% ET), beyond the levels recommended by the evapotranspiration model, generally resulted in darker fry colors for Alturas, Clearwater Russet, Russet Burbank, and Umatilla Russet cultivars. The study's findings offer nuanced guidance for potato growers. While reduced late-season irrigation can enhance fry color, the benefits are both cultivar-specific and storage temperature-dependent. Additionally, the advantages may diminish or even reverse beyond certain irrigation thresholds. This research provides valuable recommendations for optimizing water usage and fry quality, thereby assisting growers in meeting the rigorous standards of the frozen potato-processing industry.