The objective of this study was to determine the effectiveness of urea containing inhibitor of nitrification (Dicyandiamide, DCD) or inhibitor of urease (1, 2, 4 Triazole) or both on nitrate nitrogen ratio of mineral nitrogen content in soil in 4-year small-plot experiment with winter wheat (variety ´Venistar´ ) on heavy brownsoil. Effect of inhibitors was evaluated as N-NO3-/ Nmin ratio in respective soil profiles. Total dose of nitrogen (140 kg.ha-1) was applied in the form of urea at one shot (with inhibitors) or split to two (with inhibitors) or three partial rates (without inhibitors) in crucial growth stages of wheat. Soil samples were taken from the soil profiles of 0.0-0.30 m, 0.30-0.60 m and 0.60-0.90 m, respectively. Also yield of grain of wheat and natural effectiveness of fertilization were assessed. Achieved results indicate that application of inhibitors contained in urea significantly reduced N-NO3-/ Nmin ratio in soil by 11.7% (urea+inhibitor of nitrification), 10.8% (urea+both inhibitors) and 9.4% (urea+inhibitor of urease) in comparison to urea applied without inhibitors. Adverse effect of applied inhibitors on the winter wheat grain yield was not found out. These results suggest that the both examined inhibitors contained in urea fertilizer have a potential to reduce portion of nitrates on mineral nitrogen content in soil. The highest coefficient of natural effectiveness of fertilization was achieved in treatment fertilized with urea containing both inhibitors (6.860), that is there was created 6.860 kg of wheat grain per each kilogramme of applied fertilizer nitrogen in this treatment. It was owing to the fact that urea with inhibitors was applied at one shot without splitting to partial doses during growing season in comparison to application of pure urea at which the same total dose of nitrogen was split to three partial doses. Both urease inhibitors and nitrification inhibitors can be tools to manage N loss profitably in today’s economic climate.

ammonia, growth stage, nitrification, split application, urea, urease

Presentation: oral