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REGULATED DEFICIT IRRIGATION CONSERVES WATER BUT HAS LIMITED IMPACTS ON CIDER APPLE FRUIT AND JUICE QUALITY
Thesis   Open access

REGULATED DEFICIT IRRIGATION CONSERVES WATER BUT HAS LIMITED IMPACTS ON CIDER APPLE FRUIT AND JUICE QUALITY

Claire Yost
Washington State University
Master of Science (MS), Washington State University
12/2024
DOI:
https://doi.org/10.7273/000007217
pdf
Thesis Final Yost Dec 151.59 MBDownloadView
Open Access

Abstract

fruit quality juice quaity Malus domestica Borkh regulated deficit irrigation soil moisture stem water potential
The United States has experienced a resurgence in cider apple (Malus domestica Borkh.) production, with Washington State as a leading producer. However, the cider industry is experiencing several challenges, including orchards struggling to meet the demand for cider-specific cultivars, new orchards sometimes having insecure access to irrigation water or only access to high-cost municipal water, and cidermakers trying to differentiate their product in an increasingly crowded market. This project evaluated whether regulated deficit irrigation (RDI) could (1) conserve water while maintaining yield and (2) increase fruit and juice quality to help producers differentiate their products. Trees of four cultivars (Dabinett, Golden Russet, Nehou, and Porter’s Perfection) were managed with either RDI or control irrigation treatments at two distinct locations: Mount Vernon and Wenatchee, WA. In Mount Vernon, no water stress (ψstem) was detected in the trees managed with RDI, though their apple weight and fruit phosphorous decreased by 3.9% and 12.5%, respectively, while fruit firmness increased by 1.2%. In Wenatchee, a decrease in ψstem in trees managed with RDI led to reductions in fruit size (diameter and weight) in both cultivars, bloom density in ‘Golden Russet’, and leaf nutrients (N, P, K, Cu) in ‘Nehou’, as well as increased firmness for both cultivars. Fruit weight decreased by 15.5% and 33.1% for apples from ‘Golden Russet’ and ‘Nehou’ trees managed with RDI, respectively, though there was no statistically detectable decrease in yield. Irrigation was reduced by 100% in Mount Vernon and 40% and 27% for ‘Golden Russet’ and ‘Nehou’, respectively, in Wenatchee. These water reductions resulted in a net gain of $347 per hectare with RDI if irrigation was scheduled using a decision-support tool based on a calculated water balance but even a small decrease in yield (<1%) would offset this gain. No changes in juice quality for fruit from trees managed with RDI were observed in Mount Vernon, but in Wenatchee, there was an increase in specific gravity and soluble sugars. However, implementing RDI neither increased total tannins or total phenolics in the juice at either location, nor resulted in meaningful differences in the phenolic profiles of the juice.

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