ASSESSMENT OF MINERAL NITROGEN FERTILIZATION OF EARLY POTATO VARIETIES IN INTEGRATED PRODUCTION

Based on a 3-year field study, the effect of mineral nitrogen fertilization on the yield, selected tuber quality characteristics and fertilization efficiency indicators for early potato varieties grown in the integrated production system were determined. The quality of tubers was assessed according to the percentage share of tuber size and their external defects in the yield structure, starch content, dry matter, nitrates (V), protein and total nitrogen in tubers. The efficiency of fertilization with mineral nitrogen was expressed by the agronomic efficiency (AE), physiological efficiency (PE) and fertilizer recovery efficiency (FRE) by tubers. Two experimental factors were considered: nitrogen dose (0, 50, 100, 150 kg ha(-1)) and varieties (Bohun, Lady Rosetta, Lawenda, Madeleine, Magnolia). The increase in the dose of mineral nitrogen contributed to a significant increase in the yield structure of tubers with a diameter above 60 mm, the content of nitrates (V), protein, total nitrogen, the uptake of nitrogen and a decrease in nitrogen fertilization efficiency indicators. It was shown that the Lady Rosetta and Lawenda varieties were characterized by higher requirements concerning the optimal nitrogen dose than the other varieties. Nitrogen fertilization efficiency, the content of nitrates (V) and tuber greening were determined mainly by the weather conditions, while the yield, nitrogen content and uptake by tubers were determined by the fertilizing factor, and the remaining tuber quality features were shaped to the greatest extent by the genotype. In a wet year, a significantly higher tuber yield, more large tubers in the structure and higher nitrogen fertilization efficiency were obtained. In years with rainfall deficit, a higher content of total nitrogen, protein, nitrates (V) in tubers and higher nitrogen uptake were found than in a wet year.