Efficiency of nitrogen fertilization in spring wheat

An assessment of the nitrogen fertilization efficiency should not only include quantitativeand qualitative yield changes, but also an analysis of formation some indicators such as: Nharvest index (NHI), N use efficiency (NUE), N utilization efficiency (NUtE), N agronomicefficiency (NAE), N physiological efficiency (NPE) and N apparent recovery fraction (NRF).The objective of the study was the evaluation of spring wheat N fertilization efficiency undersoil conditions of Luvic Chernozem. Factors of the experiment were: cultivar (Bombona andTybalt) and level of N fertilization (0, 60, 90, 120 and 150 kg N ha-1). The application ofincreasing N rates in the wheat crop raised the grain N from 56 to 92 kg N ha-1 and theaboveground biomass N from 70 to 123 kg N ha-1 and it decreased most of the efficiencyindicators. The highest NHI value of 84%, PFNUE of 139.5 kg kg-1, NAE of 32.7 kg kg-1, NPEof 72.2 kg kg-1 and an NRF of 47% were observed for the lowest N rate of 60 kg N ha-1. TheNUtE of 92.8 kg kg-1, was at the highest level on the control plot. Every increase on N rateresulted in a significant decrease in the efficiency indicators. The cultivar factor significantlyaffected the grain and aboveground biomass N and the NAE, NPE and NRF values. Lowrainfall depths during the vegetative period favorably affected the NHI, NUtE, NAE and NPEindicators. On the other hand, excessive rainfall depths limited PFNUE, NAE, NPE and NRF.