A significant reduction in nitrogen (N) losses from agricultural fields will make a positive impact on the environment. Managing nitrogen for the optimum application provides economic benefits as well as environmental protection. This study presents a model
that was developed to determine the optimum ratio of N to yield based on N sensor indices in winter wheat. A quadratic polynomial model was used to characterize the relationship between N and yield for the optimum N rate. The N was applied to the Bezostaja
and Ahmetaga wheat varieties at 0 kg N ha−1, 80 kg N ha−1, 120 kg N ha−1, 160 kg N ha−1 and 200 kg N ha−1 ratios. The results showed that the most economical mean estimated N rate was 167.6 kg N ha−1 for Bezostaja and 206 kg N ha−1 for Ahmetaga.