Articles
NITRATE CONTENT IN LEAFY VEGETABLES AS RELATED TO NITROGEN FERTILIZATION IN CROATIA
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 content in lettuce and radicchio without significantly increasing the yield, although all the nitrate values were still below the maximum limit prescribed by the FAO 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 kg/m2 of radicchio grown outdoors were achieved by fertilizing with 80–160 kg of N per hectare.
The low levels of nitrate achieved in lettuce (1820–2237 mg NO3/kg FW), and less than 1000 mg NO3/kg FW in radicchio grown outdoors, are, in our opinion, even more important than the high yields.
All this indicates that Croatia, with its 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.