THE EFFICIENCY OF USING NITROGEN FERTILIZERS IN WHEAT CROP

Nitrogen has its undeniable role in increasing crop productivity and quality. However, used improperly, it can cause serious environmental damage. Increasing the efficiency of the use of chemical nitrogen fertilizers (NUE) is a goal of the future¸ necessary for a sustainable and competitive agriculture. The wheat crop studied is part of a long-term experiment, established in Lovrin in 1967. The experimental factors studied are: factor A - nitrogen, with the following graduations: N0, N30, N60, N90 and N120 and factor B - phosphorus, with the following graduations: P0, P40, P80, P120 and P160. From the combination of the two studied factors  results  25 experimental variants,  placed in the field according to the method of subdivided plots, in four repetitions. Chemical fertilizers with phosphorus - 46% superphosphate - were administered to the wheat crop in autumn and were incorporated under the basic plowing. Nitrogen fertilizers - 33.5% ammonium nitrate - were applied in fractions: 40% of the dose at start of vegetation, in the spring and 60% at straw elongation. The wheat culture is part of a three-year crop rotation - soybeans-wheat-corn. Following in rotation after soybeans, no nitrogen fertilizers were applied at the establishment of the crop. The variety studied is the Ciprian variety, created at SCDA Lovrin. For the evaluation of NUE, Plant N Uptake, Nitrogen Use Effciency and Partial Factor Productivity were analyzed in this paper. In the climatic conditions of the two experimental years, a distinctly significant positive correlation is established between the nitrogen dose administered and production, the value of the correlation coefficient being 0.56 **. Between the nitrogen dose, the protein content and the amount of protein per ha the correlation is very significant, with the following values ​​of the correlation coefficients: r = 0.96 *** (for protein) and r = 0.90 *** (for N uptake). Nitrogen use efficiency correlates negatively, very significantly, with the administered dose - r = -0.87 ***. This study also reveals the importance of phosphorus in the absorption and accumulation of nitrogen in wheat caryopsis. The amount of nitrogen accumulated increases with increasing dose of phosphorus, up to 80 kg ha-1, with the gradual reduction of the amount accumulated to high values ​​of phosphorus administered (120 kg ha-1 and 160 kg ha-1, respectively).