Two field experiments were conducted at Sakha Agricultural Research Station, North Delta, Egypt during two successive growing seasons (2010-2011 and 2011-2012) to study the effect of nitrogen fertilization with and without K and B application on wheat yield in addition to evaluate quantitatively the response of wheat grain yield to fertilizer application using a polynomial quadratic equation. Five N levels ( 0, 30, 60, 90, and 120 kg N fed^-1) were applied as a main plots, with 2 levels of K ( 0 and 50 kg K₂O fed^-1) as sub-plot, and B solution at 0.1% concentrationsprayed after 70 days from sowing as sub-sub plots. The cultivated wheat variety was Sakha 69. The main results could be summarized as follows: 1- Increasing N levels up to 90 kg fed^-1 led to a significant increase in the grain yield. Also, the grain yield was increased with potassium application in average by 2.5 %. Foliar application of boron resulted in increasing the grain yield in average by 2.48%. 2- The estimated values of the maximum N rate (x_max) were 2.76, 2.83, 2.78 and 2.77 units of N fed^-1. (one N unit = 30 kg) for the treatments of  N only (A), N with B (B), N with K(C) and N with B and K(D), respectively. The estimated values of maximum wheat grain yield (Y_max) (17.051, 17.586, 17.788 and 18.140 ardab fed^-1 for the four treatments, respectively) were increased by applying K and B fertilizers. 3- The economic optimum yield (Y_opt) was obtained by applying the economic optimum rates (x_opt). The values of x_opt were 2.63, 2.70, 2.65 and 2.64 N units fed^-1 for the four treatments, respectively. The values of Y_opt were 17.03, 17.57, 17.76 and 18.13 ardab fed^-1 for the previous mentioned treatments, respectively. The net returns of using N fertilizer were 2612.80, 2753.82, 2766.34 and 2865.10 LE fed^-1 for the four treatments, respectively. Hence, it could be concluded that the maximum and optimum wheat grain yield (Y_max and Y_opt) were increased by applying K and B fertilizers. 4- Relative efficiency of applied N fertilizer (E_X) with different treatments could be arranged in the following descending order: D > C > B > A. The highest efficiency of soil N (ex_s) was obtained under treatment B. The highest value of soil N (x_s) (1.486 unit fed^-1) was obtained with A treatment. The contribution of applied N fertilizer increased with increasing N level and the highest value of applied N fertilizer contribution was obtained under D treatment. Also, the contribution of soil N decreased with increasing N application level up to 120 kg fed^-1 (N₄). The net return due to Boron spraying was 299.8 L.E fed^-1. Generally it could be concluded that increasing N level up to 90 kg/fed led to a significant increase in wheat grain yield. The maximum, optimum wheat grain yield (Y_max and Y_opt), N use efficiency and the net return were increased by applying K and B fertilizers. Also the contribution of soil N decreased with increasing N application level up to 120 kg fed^-1.