Effect of fertility and irrigation on sugar content in potato tubers

The desirable sugar content in potato tubers is 0.5-1.5 %. The effect of cultural practices on the technological quality of potato tubers is of exceptional significance. Thus the objective of this investigation was to study the effect of fertilization with increasing doses of nitrogen (0-200 kg per ha) and potassium (0-200 kg per ha) - both with and without irrigation - on the content of sugar in tubers of young and physiologically matured potatoes. The study was conducted from 1988-90 with the varieties Kennebec and Desiree. Sugar content was lower in both varieties in conditions of irrigation, both with early harvesting and in the period of full maturity. Increasing doses of potassium was found to have a positive effect on the decrease of sugar content in the tubers of young potatoes (r=0.89*), and in the period of harvesting matured potatoes (r=0.90*) of both varieties. Additionally, the effect of nitrogen was found to be highly significant in the period of harvesting for the matured Kennebec potato variety without irrigation (r=0.99**).