J. Elem. s. 661–672 DOI: 10.5601/jelem.2014.19.3.704 SUITABILITY Of SOME NITROGEN fERTILIZERS fOR THE CULTIvATION

Early cabbage was grown in a field experiment in two treatments, with and without weed control, to test the following fertilizers: ammonium nitrate and Entec 26-a, a new formula ni-trogen fertilizer containing a DMPP nitrification inhibitor, applied in single preplant or split doses, and calcium cyanamide (Perlka), supplied only prior to the planting of cabbage. All the sources of N were used in amounts supplying 150 kg N ha-1. The fertilizer Perlka was applied 2 weeks before planting cabbage transplants, while Entec 26 and ammonium nitrate were intro-duced to soil 3 days before that. All the fertilizers were incorporated into the soil by harrowing. In the treatments with split N application, top dressing was conducted just after the cabbage plants were uncovered, which took place 3-4 weeks after transplanting. The experiment was established in a one factorial design with four replications. The results proved high efficiency of nitrogen fertilization, which – when applied at a dose of 150 kg N ha-1- enhanced the yield of early cabbage by about 50 % compared to the treatment without N fertilization and weed control. Ammonium nitrate and Entec 26 appeared to be equ-ally valuable sources of this nutrient, both in single and split doses, in each year of the investi-gation. Calcium cyanamide produced the highest marketable yield of heads with a significantly lower mean content of nitrates in edible parts. Another big advantage of this N source is its high efficiency in reducing weed infestation during the whole vegetation period