THE EFFECT OF POLIMAG S FERTILIZER ON THE MACRONUTRIENT CONTENT OF THE EDIBLE PARTS OF THREE WELSH ONION (ALLIUM FISTULOSUM L.) CULTIVARS

Welsh onions are characterized by a relatively high storage potential, high nutritional value and mild flavor, which contribute to their growing popularity among consumers. The aim of this study was to determine the effect of Polimag S fertilizer applied at two doses on the macronutrient content of edible parts of three Welsh onion cultivars. A two-factorial field experiment was performed in a randomized block design with three replications. It was set up in the Experimental Garden of the University of Warmia and Mazury in Olsztyn, and conduccted in 2010-2011. The experimental factors were: (1) Welsh onion cultivars Long White Ishikura, Parade and Performer, grown from seedlings for bunch harvest, and (2) the application of mixed fertilizer, Polimag S, at two doses of 0.072 kg m(-2) and 0.144 kg m(-2). The seedlings were grown in a greenhouse, where each year seeds were sown in boxes (50 cm x 30 cm), between 14 and 20 March, to grow seedlings. At the two- or three-leaf stage, they were planted out in a field between 17 and 26 April. Forty-two seedlings were planted on a plot, at the 20 cm x 30 cm spacing. Polimag S, applied as a supplemental fertilizer at two different doses, was mixed with soil immediately before the transplanting of seedlings. A single harvest was carried out manually. Marketable yield consisted of healthy Welsh onion plants, with thickened leaf-bases of more than 1 cm in diameter, free from diseases, pests and mechanical damage. The chemical composition of Welsh onion plants was evaluated immediately after harvest. The concentrations of macronutrients (total N, P, K, Mg, Ca, S) were determined in edible parts of Welsh onion plants. Statistical analysis revealed no significant effect of a cultivar on the macronutrient content of whole Welsh onion plants, scapes and leaves. Leaves were characterized by the highest macronutrient concentrations. Polimag S at a 50% dose contributed to a significant increase in the total nitrogen and phosphorus content of whole plants. Wide Ca:Mg, Ca:P, K:Mg and K:(Mg+Ca) ratios were noted in whole Welsh onion plants.