Irrigation method and harvest time affect storage quality of two early-season, tablestock potato (Solanum tuberosum L.) cultivars

- Storage quality was evaluated for two tablestock potato (Solanum tuberosum L.) cultivars ('Fabula' and 'Red LaSoda') grown in a sub-tropical climate under three irrigation methods: seepage, surface drip, or sub-surface drip, and harvested over a three-week period after vine kill.
- Tuber periderm maturation of both cultivars was a key determinant of tuber quality at harvest and during subsequent storage. Tubers harvested one week after vine kill were less mature, resulting in significantly higher weight loss and lower firmness after 14 days of storage, compared to later harvest times.
- 'Fabula' tubers harvested one week after vine kill were also compositionally less mature than those from the later harvests, as reflected by significantly higher losses in dry matter content and ascorbic acid content with increased storage time, irrespective of the irrigation method.
- In contrast to 'Fabula', 'Red LaSoda' plants were compositionally more mature at harvest; dry matter content and ascorbic acid content remained constant during storage.
- 'Fabula' and 'Red LaSoda' tubers grown under drip irrigation had comparable harvest and storage quality to those grown under seepage irrigation when harvested two to three weeks after vine kill and stored at 10 °C, 80-85% RH.

Storage quality was evaluated for two tablestock potato (Solanum tuberosum L.) cultivars grown in a sub-tropical climate under three irrigation methods and harvested over a three-week period. Early-maturing 'Fabula' and 'Red LaSoda' potatoes were irrigated with either seepage (SE), surface drip (SD), or sub-surface drip (Sub-SD; tape buried 15 cm) irrigation, during two spring seasons. Inherent potato seed dormancy in 'Fabula' resulted in delayed and non-uniform plant establishment. At horticultural maturity, vines were killed using a chemical desiccant to promote tuber periderm maturation. Tubers were harvested 1-3 weeks after vine kill (H1, H2, H3), and tuber quality was evaluated weekly during 14 days storage at 10 °C and 80-85% relative humidity (RH). In 'Fabula', H1 tubers, with more immature periderms, had the highest weight loss (5.3%) and were significantly less firm after 14 days of storage. Average cumulative weight loss for later harvests was 1.4% and tubers remained firm throughout storage. Pulp (cortex, xylem, perimedullary and pith tissue) ascorbic acid content of H1 'Fabula' tubers decreased during storage; however, it was higher in SD and Sub-SD (17.1 mg 100 g−1) than in SE tubers (11.8 mg 100 g−1) after 14 days. There were no significant differences in whole tuber or peel ascorbic acid content during storage; average was 20.1 mg 100 g−1 and 7.2 mg 100 g−1, respectively. Although dry matter content in the peel decreased with increased delay to harvest time for all irrigation methods, it remained constant throughout storage. Average dry matter content, for all harvest times, during storage was 16.7%, 8.8% and 14.8% for whole tuber, peel and pulp tissue, respectively. 'Red LaSoda' plants tend to grow faster than 'Fabula' and, therefore were compositionally more mature at harvest; no significant differences in dry matter or ascorbic acid content were observed before or during storage. However, similar to 'Fabula' tubers at H1, firmness decreased by 7 days in storage for all irrigation methods, possibly due to excessive fresh weight loss. Harvest and storage quality of 'Fabula' and 'Red LaSoda' grown under either SD or Sub-SD was comparable to SE at H2 and H3, with the potential to significantly reduce irrigation water usage during production.