Effect of nitrogen and potassium application rates on nitrogen use efficiency and tuber minerals content in central high lands of Ethiopia

An experiment was conducted on a Nitisol of Holetta agricultural research and Jeldu Sub-center  using three factors such as potato varieties (Belete, Jalenie and Gudanie), nitrogen rates (87, 110 and 133 kg/ha) and potassium oxide rates (0, 34.5, 69 and 103 kg/ha) that were arranged on randomized complete block design with three replications. The data were subjected to Proc GLM model of SAS software version 9.2. Higher tuber nitrogen content, uptake and utilization was obtained from Holetta location than Jeldu. Increasing nitrogen fertilizer from 87 to 133 kg/ha reduced the tuber nitrogen uptake and utilization efficiency by 75.56 and 75.49%, respectively. The interaction between variety and location also highly significantly affected tuber nitrogen content and nitrogen utilization efficiency. The interaction between nitrogen and variety affected tuber nitrogen in percent and protein content highly significantly. The highest tuber nitrogen and protein content was obtained from Belete and Gudenie varieties at a rate of 110 kg/ha nitrogen. From these results, it can be concluded that, the interaction between nitrogen and potassium rates did not affect significantly any parameter measured in this experiment, while nitrogen, varieties, interaction of location with variety showed significantly different nitrogen use efficiencies and tuber minerals content. Key words: Gudenie, Belete, Jalene, potassium, nitrogen rates.