SUITABILITY OF SOME NITROGEN FERTILIZERS FOR THE CULTIVATION OF EARLY CABBAGE

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 nitrogen 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 introduced 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 equally valuable sources of this nutrient, both in single and split doses, in each year of the investigation. 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.