The accumulation of carotenoid compounds in carrot (Daucus carota L.) roots of five cultivars, in relation to different nitrogen fertilization levels was investigated. The experiment was carried out at the Warsaw University of Life Sciences. Carrot cultivars ‘Karotan’ F1, ‘Trafford’ F1, ‘Krakow’ F1, ‘Komarno’ F1 and ‘HY 7842’ were used in the study. Nitrogen fertilization was applied as urea form, in doses ranging from 0 to 120 kg N ha–1, and on two terms: pre-sowing and in the middle of the growing season. The carrot seeds were sown at the beginning of May and the roots were harvested in mid-October at maturity. Total carotenoids and β-carotene contents in the carrot roots were determined after the harvest by means of the standard spectrophotometric method. CIE L*a*b* colour parameters of the roots and the juice, as well as dry matter in the roots were determined. Results of the experiment showed that carotenoid accumulation in the roots was significantly affected by carrot genotype. ‘HY7842’ carrot showed the highest accumulation of total carotenoids and β-carotene. Nitrogen in the rates applied, did not significantly influence carotenoid content in the roots. Moderate correlation between carotenoid content and colour a* parameter (redness intensity) of the roots and the juice was found.

Quality of Carrots Grown for Processing as Affected by Nitrogen Fertilization and Harvest Term In 2007-2008 the effect of nitrogen fertilization and harvest term on quality of two carrot cultivars was investigated. The field experiment was carried out in Żelazna Experimental Station of Warsaw University of Life Sciences. Karotan F1 and Trafford F1 cultivars, commonly grown for juice industry, were the objects of the experiment. Carrot seeds were sown at the beginning of May. Nitrogen fertilization was applied in five rates, ranged from 0 to 120 kg·ha-1 and in two terms — before sowing and in the middle of growing season. Roots were harvested in three terms: mid-September, mid-October and the first decade of November. After harvest there were determined: nitrates (NO3) content in carrot roots and juice, soluble solids, colour parameters of juice in CIE L*a*b* system. The dose and the term of nitrogen fertilization influenced nitrates content in carrots, and the highest NO3 concentration was found in carrots fertilized with 120 kg·ha-1 of N before sowing. Karotan showed higher nitrates accumulation than Trafford. The content of nitrates in the roots was markedly higher than in carrot juice. Nitrates content in carrots decreased with delaying of harvest time, in opposite to soluble solids content. Soluble solids content and colour parameters of carrot juice were not affected by nitrogen fertilization, but the lowest L*, a* and b* values were observed at the last term of harvest.