Technical Abstract: Agricultural producers make fertilizer decisions based on recommendations from extension personnel and/or consultants established by the best available data; however, optimal nitrogen (N) recommendations can vary depending on the functional form used to estimate yield response functions. Applying too much or too little N fertilizer can negatively influence producer profits, as well as environmental conditions. The objective of this research is to evaluate different crop response models for cotton and compare the resulting economically optimal rates of N fertilizer. The overall conclusion, when analyzed by year, is that the appropriate functional form differs by year. For 2006, 2007, and 2008, the preferred functional forms were the square root, linear, and quadratic functional forms, respectively. In the 2008, the difference in the expected revenue above N costs between the asymptotic maximum and the economic optimal was approximately $1 per acre, demonstrating that, for this data, in 2008, there was little difference between the asymptotic maximum and the economic optimal.