NITROGEN MANAGEMENT FOR POTATOES BY USING RAPID TEST METHODS

To evaluate the efficiency of rapid field tests for potato nitrogen management, five N fertilizer treatments (0, 100, 150, 200 and 250 kg N ha-1) were applied on three cultivars and replicated three times. Representative leaf samples were collected three times during vegetation at 10 day intervals, and nitrate in the petiole sap was immediately measured with a Cardy ion meter. Approximately 30 leaf chlorophyll readings were also taken. At the same time petiole samples were collected, with a portable, hand held Hydro N-tester chlorophyll meter. Petiole sap nitrate concentration and chlorophyll content index (CCI) increased with increasing fertilization levels and decreased as the season progressed. Highest correlations between the amount of nitrate nitrogen and chlorophyll in leaves were observed at approximately 50 days after planting. Furthermore, the methods were highly correlated. Yield was not related to the amount of petiole sap nitrate and chlorophyll content index during the vegetation.