Growing herbal plants is aimed at obtaining high yield of raw material with high contents of biologically active substances, as well as other important compounds, also of nutritional character. In the years 2008–2010 (February – May) studies were conducted on the relationship between cultivar, nitrogen dose (NH₄NO₃), potassium dose (K₂SO₄), and some components of chemical composition of basil herb. The study subject were basil plants of two Polish cultivars: Kasia and Wala, as well as the green-leaved form, popular on the domestic fresh herb market. Basil was grown in the greenhouse, in pots of the capacity of 4 dm³. Four doses of nitrogen and two doses potassium were applied. In the herb collected during full flowering dry matter, N-NH₄ and N-NO₃, nitrogen total, potassium and protein contents were determined. It was demonstrated that average dry matter contents in the herb of examined basil plants was 13.20% and significantly depended on the cultivar and dose of applied nitrogen. The most (15.47%) dry matter was found in the herb of Wala cultivar plants. The increasing nitrogen doses caused the increase of protein contents in basil herb. The most (26.13% d.m.) of protein was found in the herb of plants fed with the highest dose of nitrogen. Plants receiving the most potassium had more (23.24% d.m.) protein in the herb than plants receiving less of that nutrient (22.31% d.m.). Mean content of nitrate nitrogen in the examined herbal material was 0.78% d.m. Plants of Wala cultivar had significantly lower (0.66% d.m.) amount of nitrate nitrogen than the remaining ones. Additionally increased contents were demonstrated of nitrogen (total, ammonium, nitrate) and potassium in basil herb as an effect of increased nitrogen dose.

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