Effect of nitrogen source and rate on potato tuber external and internal physiological disorders

Athyna N. Cambouris1, Mervin St. Luce1, Noura Ziadi1, Bernie J. Zebarth2 and Isabelle Perron1

1Agriculture and Agri-Food Canada, 2560 Hochelaga Boulevard, Quebec City, QC, Canada, G1V 2J3, [email protected]

2Agriculture and Agri-Food Canada, 850 Lincoln Road, PO Box 20280, Fredericton, NB, Canada, E3B 4Z

Abstract

Potato (Solanum tuberosum L.) tuber quality is an important factor that can affect its market value. We investigated the impact of nitrogen (N) fertilizer source and rate on external and internal defects of potato tubers across five growing seasons (2008 – 2012) under irrigated conditions on sandy soils in Quebec, Canada. The treatments included an unfertilized control, and three N sources [ammonium nitrate (AN), ammonium sulphate (AS) and polymer-coated urea (PCU)] applied at four rates (60, 120, 200 and 280 kg N ha-1). The PCU was applied 100% at planting and the AN and AS were applied 40% at planting and 60% at hilling. Yield of misshapen tubers was greater and there was a lower incidence of rhizoctonia at higher N rates. Conversely, common scab and brown spot were more prevalent at higher N rates. Yield of misshapen tubers and the presence of hollow heart were greater for AN and PCU than AS. There was also a greater occurrence of common scab for PCU as compared to AN and AS. Additionally, brown spot tended to be more prevalent when PCU was used. Our results suggest that while PCU may give similar potato tuber yields to AN and AS, there may be a slightly greater tendency for increased common scab when PCU is applied. Overall, this study showed that N fertilizer rate and source are important factors that can influence the occurrence of external and internal physiological disorders of potato tubers, and thus tuber marketability.