The field experiment was conducted in the years 2003-2005 in Felin Experimental Station of the University of Life Sciences in Lublin (Poland). The following factors were taken into consideration in the studies: 2 fennel cuitivars – Rudy F1 and Zefa Fino, 3 terms of sowing the seeds – April, May, June; 3 kinds of shields – covering the soil with black polyethylene foil (PE), covering the soil with black polypropylene unwoven (PP 50 g m-2) and flat covering the plants with white polypropylene unwoven (PP 17 g m-2), as well as control (without cover); 3 bulb harvest terms: after 10, 12 and 14 weeks from sowing; bulb weight: <200 g; 200-350 g; >350 g.
The applied mulches, made of PE foil and PP50 unwoven, as well as shielding the plants with PP17 unwoven did not significantly affect the contents of examined nutrients in the fennel bulbs and leaves. Fennel leaves contained more dry matter, N-total, Ca and Mg than the bulbs. The bulbs were more abounding with P and K. The bulbs of plants from June sowing contained the most N-total, nitrates, K, Ca and Mg. In the leaves the most N-total and nitrates were determined after June sowing term, and Ca and Mg after April sowing. Bulbs and leaves of Rudy F1 cuitivar contained more N-total and Ca than these of Zefa Fino cultivar. As the harvest term was delayed, the contents of N-total, P, K, Mg and nitrates in the bulbs decreased, whereas the dry matter content increased. The buibs with weight < 200 g contained the most N-total, potassium and nitrates, and the least phosphorus. The least potassium, nitrogen and nitrates was found in the bulbs with weight > 350 g.