Natural factors and human intervention, especially fertilization, change the ion dynamics in soil and substrates. Nutrients are often available in different chemical forms (mineral and organic), and as for iron, both forms, i.e. sulfates and chelates, are commonly used. The purpose of the study was to determine the influence of different sources and levels of iron, on the content of macronutrients in leaves of lettuce cultivated in peat substrate. The experiments were conducted in the spring and autumn season in a three-year cycle. They were set up under controlled, greenhouse conditions. Six sources of iron were applied (two sulfates and four chelated forms). The total content of N, P, K, Ca, Mg, S and Na was determined. The results were analyzed statistically with the Newman-Keuls test at a significance level of level α = 0.05. The differentiated iron nutrition (both source and level) influenced the mineral composition of lettuce. In the spring cultivating season, mineral forms of iron in comparison to a chelate, caused significantly lower content of nitrogen and potassium. In the autumn cultivating season, after an application of mineral forms of iron compared to chelated ones, lettuce plants contained significantly more calcium and sulfur. To describe the relationship between the experimental factors, correlation and curvilinear regressions were determined. The iron nutrition significantly influenced the content of macronutrients in lettuce leaves. Negative correlation between the level of iron in the substrate and the content of phosphorus and calcium in the leaves was found. Positive correlation was found between the content of iron in the substrate and the content of sodium in the plants.  

24.1.2019