The aim of the research, conducted in 2012 – 2014, was to investigate the effect of mineral nitrogen on the total yield and quality of tubers of early varieties harvested 75 days after planting (DAP) and after tuber maturity, as well as to establish fertilization efficiency indices. Nitrogen utilization efficiency was expressed as agronomic efficiency (AE), physiological efficiency (PE) and fertilizer recovery efficiency (FRE) in tubers. Two experimental factors were researched: nitrogen level (0, 50, 100, 150, 200 kg ha-1) and varieties (Altesse and Gwiazda), tested under different weather conditions. The total yield of fresh weight between the nitrogen doses ranged from 20.3 to 26.6 t ha–1 when harvested 75 days after planting, and from 31.9 to 45.9 t ha-1 when harvested after tuber maturity. Increasing nitrogen doses caused an increase in tuber yield, content of nitrates (V), nitrogen uptake (NUp), but led to a decrease in agronomic (AE) and physiological (PE) efficiency, fertilizer recovery efficiency (FRE) and starch content. The quadratic function parameters proved that the variety Gwiazda needed more nitrogen than the variety Altesse. Between the dates of the harvest, the largest differences were found in relation to the nitrogen uptake with tuber yield. On average for the both varieties, all doses and years, harvest of tubers after maturity resulted in higher AE (by 41 kg kg-1), PE (by 2 kg kg-1) and FRE (by 16%) than when tubers were harvested 75 DAP. The year 2013 was characterized by the highest reduction in the yield of tubers, nitrogen uptake, efficiency of fertilization and fertilizer recovery efficiency by the tested potato varieties on both harvest dates.

24.4.2019