Cold storage, reconditioning potential and chip processing quality of spring potato (Solanum tuberosum L. cv. Hermes) tubers in response to differential nitrogen fertilisation

BACKGROUND: Crop management has been implicated in tuber sugar accumulation and potato processing quality. However, reports on potato postharvest behaviour, tuber composition and processing quality in response to crop nitrogen (N) fertilisation have been sparse and inconclusive. In this study, chipping potato cv. Hermes was treated with four preplanting N rates (01 100, 200 and 300 kg ha(-1)) to evaluate the effect of N fertilisation on sugar accumulation profiles and processing quality at harvest, after cold storage at 4.5 degrees C for up to 200 days and after reconditioning at 16 degrees C for 10-30 days. RESULTS: Preharvest leaf petiole analysis and tuber nitrate analysis at harvest confirmed crop response to N rates. At harvest, tuber specific gravity decreased marginally beyond 200 kg N ha(-1). Chip colour as well as tuber sucrose and reducing sugar (RS) content was unaffected by N fertilisation rate. During cold storage and reconditioning, tuber fresh weight loss and sprout growth were unaffected by N rate, while its effect on tuber sugar levels was either statistically or practically insignificant. Tuber sucrose and RS contents correlated highly with chip colour (r = -0.729, P < 0.001 and r = -0.791, P < 0.001 respectively). Importantly, postharvest chip colour was also unaffected by N rate, though it declined markedly with the onset of cold storage and improved significantly throughout reconditioning. Differences in chip colour between years were limited but potentially critical in meeting the commercial standard. CONCLUSION: Completion of physiological crop senescence of the spring potato crop under Mediterranean climatic conditions seems to mitigate the potential interference of preplanting N fertilisation with tuber maturation and subsequently cold storage performance, reconditioning potential and processing quality. (C) 2009 Society of Chemical Industry