INFLUENCE OF NITROGEN ON POTATO PRODUCTIVITY AND NUTRIENT USE EFFICIENCY

Yield and quality of potato depend on nutrient availability in soil, especially regarding nitrogen. Nitrogen (N) is a very dynamic plant nutrient and its uncontrolled application can considerably raise the price of agricultural production. If N is insufficiently utilised by plants environmental pollution can occur. The aim of the study was to investigate efficiency of nitrogen fertiliser use by potato. The field trials were carried out at the State Priekuïi Plant Breeding Institute from 2009 till 2012. Nine fertilisation variants were applied: no fertilisation; PK dose to provide potato yield of 40 t ha-1; and the remaining seven variants with a PK dose plus plus increasing N amount from 30 to 210 kg ha-1. The results of the four-year experiment years indicated that an increase in nitrogen fertilizer rate up to N120 kg ha-1 increased the potato yield. Nitrogen fertilizer rates should be applied depending on potato variety and planned use of the grown potato crop. Tuber nitrogen content increased with nitrogen fertilizer level from 1.09% in the treatment N0PK up to 1.53% in treatment N120, and practically remained at that level in treatments with higher N application levels. Nitrogen content in potato foliage was twice as high as that in tubers and continuously increased with the N amount applied, and particularly with higher nitrogen fertilizer rates of N150–210. In regard only to tuber yield, the N utilization coefficient at a nitrogen fertilizer rate up to N120 was on average 0.60. A further increase in nitrogen rate reduced the N utilization coefficient with each successive step.