engleski

Nitrate content in leafy vegetables as related to nitrogen fertilization in Croatia

Research on the influence of nitrogen fertilization on the nitrogen content and yield of 1ettllce (Lactuca sativa L.) and radicchio (Chichorium intybus L. var. joliosum) was carried out on several locations in Croatia over a: number of years. Research on lettuce was carried out in the winter growing season in greenhouses in Zadar in 1985 and in Bjelovar and Durdevac in 1989, while the research on radicchio started in Zagreb in 1991 and was performed outdoors in the summer growing season. The research results indicate that increased nitrogen fertilization led to an increased nitrate tbntent in lettllce and radicchio without significantly increasing the yield, although all the nitnite values were still below the maximum limit prescribed by the FAG standards and most European countries. Yields of 5.35-6.29 kg/m2 of lettuce grown in a greenhouse (during the winter season) and 2.1-2.5 kgim2 of radicchi~grpwn outdoors were achieved by fertilizing with 80-160 kg of N per hectare. The low levels of nitrate achieved in lettuce (1820-2237 mg N~/kg FW), and less than l(xx) mg N~/kg FW in radicchio grown outdoors, are, in our opinion, even more important than the high yields. All this indicates that Croatia, with it.. existing supply of nutrients in substrates and soils can, under the prevailing agro -ecological conditions and regardless of the growing season and location, produce vegetables for the most demanding world markets.

Nirtogen fertilization; nitrate content; lettuce; radicchio red

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