Nitrogen and calcium are the two elements, among other main nutrients, responsible for proper nutrition of plants. The experiments conducted with lettuce of the Omega F₁ variety aimed at an analysis of differentiated methods of nitrogen and calcium carbonate fertilization on the general crop yield and its biological value. After the plants were collected, the fresh weight of the plants, the dry mass, the vitamin C content, extract and protein contents were measured. After the vegetation period of plants samples of medium were collected and, with use of 0.03 M extract of acetic acid, the contents of mineral nitrogen, phosphorus, calcium and magnesium were determined, as well as the pH and EC values of the medium measured. The crop yield of fresh leaves mass was significantly dependent on the used dose of nitrogen and calcium carbonate. The largest lettuce crop yield was recorded in objects fertilized with 0.4 g ∙ dm^-3 of nitrogen and the higher dose of calcium carbonate (283 g∙plant^-1). The vitamin C, extract and protein contents were dependent on the dose of nitrogen. The largest quantity of vitamin C characterized the lettuce plants fertilized with the largest dose of nitrogen and the higher dose of calcium carbonate (33.7 mg∙100 g^-1 fr. m.). The application of calcium carbonate in 14 g ∙ dm^-3 causes the calcium content of the medium to rise. The EC value of the medium was largely arisen under the influence of the mineral nitrogen and varied between 1.33 and 1.96 mS∙cm^-1.

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