This work shows the results of nitrate analysis of the annual priority actions from 2006 to 2014. 95 % of 1 191 samples complied with the maximum levels laid down in EU food legislation. 16 % of fresh spinach exceeded the maximum level, more often at the beginning and at the end of the harvest season (April and September). Deep-frozen spinach, on the other hand, showed significant lower levels of nitrate.
The level of nitrate was significantly higher in lettuce grown under cover when compared to lettuce grown in the open air. In 67 % of lettuce grown in the open air the nitrate content was not higher than half of the maximum permitted level. In contrast, only 40 % of lettuce grown under cover were below 50 % of the maximum level. In “Iceberg” type lettuce the proportion was 73 % when grown in the open air and 56 % when grown under cover, respectively.
Nitrate levels in lettuce and spinach of organic farming were considerably lower than in samples of conventional cultivation.
Trend analysis showed a significant increase of nitrate concentration of “Iceberg” type lettuce grown under cover. In contrast, nitrate level in lettuce (excluding “Iceberg”) grown under cover decreased significantly. Nitrate content of deep-frozen spinach also decreased significantly from 2006 until 2014.