Among field crops, potato (Solanum tuberosum L.) has the fourth place in concern to the total yield amounts after wheat, rice and corn. Apart from the high yield levels caused by increased requirements in marketing, high quality has also outstanding importance. For this, balanced nutrient supply based on soil testing results is essential. Deficient and excess use of fertilizers may also cause numerous problems related to yield levels and tuber health conditions. Considering the actual prices of fertilizers, producers are interested in achieving target yields by appropriate fertilization and agrotechnics avoiding excessive use of fertilizers and environmetal risks at the same time.

The main subject of our experiment was to study the growth, vegetative parameters, flowering, tuber initiation of potato (Solanum tuberosum L.), cv. Hópehely as affected by optimum and imbalanced NPK nutrient supply.

A small plot field experiment was carried out at the Experimental Station of Potato Research Center at the University of Pannonia, Georgikon Faculty. Apart from the unfertilized control, effects of 6 treatmet combinations were studied and results were compared to literature data.

During our study, several vegetative parameters were determined by sampling. Leaf analyses were done at the start of flowering, nutrient element content of tubers were determined at the harvest.

From the results it was evident that plants grown under nutrient deficient conditions were weak, leaves were chlorotic, flowering and tuber yield formation has started earlier. Results showed highest values in the N1P1K2 treatment: maximum of average fresh weight, leaf diameter and length were found with the higher rate of K. With the increased leaf area, potato plants were able to produce higher amounts of assimilates required for optimum tuber yield. This was also due to the better supply of potassium.

Nitrogen and potassium content of leaf samples were significantly higher compared to the unfertilized control. Significant differences in yield quantities were observed both compared to the control and among the treatments applied. Differences were significant in the N and K element content of tubers. From the results of the correlation analyses it was evident that there was a close significant relationship between leaf fresh weight and tuber yield level.

Keywords: potato, NPK fertilization, small plot experiment, production of crop