A greenhouse pot experiment on humic sandy soil from Pallag was conducted to investigate the effects of different plant nutrition methods (different cultivation methods) on certain nutritional indicators of lettuce (Lactuca sativa L. var. capitata), such as antioxidant capacity, nitrate-, P-, K-, Ca-, Mg-, Mn-, Zn- and Cu-content.

In the experiment lettuce was grown in 45 pots, three plants per plot. NPK fertilizer (as integrated cultivation method) and mature cattle manure (as organic cultivation method) were applied as treatments. 15 pots were control pots, 15 pots were treated with NPK fertilizer and 15 pots were treated with cattle manure. Plant samples were collected five times during the growing season. The experiment was finished at the marketable state of lettuce. We measured the antioxidant capacity (FRAP), nitrate- and nutrient content of lettuce.

Based on the obtained results, it can be concluded that in our conditions the methods of plant nutrition affected some nutritional indicators of lettuce. By the last stage of the growing season the FRAP values of plants which were treated with organic manure were higher than those treated with mineral fertilizer. At the same time the nitrate content of lettuce treated with mineral fertilizer was higher. The nitrate content of plants in our experiment did not exceed the allowed limit. Our results show that plants treated with organic manure contained higher amount of phosphorus, potassium and magnesium compared to control plants and to ones produced with mineral fertilizer. On the contrary the calcium content of plants was higher in organic manure treatment.

Among the micronutrients we found significant differences in the manganese content of plants. The manganese content of plants treated with mineral fertilizer was higher than the ones treated with organic fertilizers. This may be related to the soil acidification effect of mineral fertilizers.

Keywords: organic production, nutrient content, antioxidant, lettuce