A Field experiment was conducted in a sandy soil at Anshas, El-Sharkia Govemorate, to investigate the effect of applying either coal refuse or town refuse ash at the rates of 0, 10, 20, 40, 60 and 80 ton/fed on some soil properties and yield of sesame. The obtained data revealed that soil bulk density, penetration resistance and hydraulic conductivity decreased with increasing application rates of either coal refuse or town refuse ash, while the maximum water holding capacity was increased. The obtained data showed that sesame seed yield increased with increasing either coal refuse or town refuse ash rates up to 80 ton/fed. The average yields were 2.33, 3.50, 5.06, 7.26, 8.53 and 9.96 kg/plot (plot = 9 m2) for coal refuse addition rates of 0, 10, 20, 40, 60, and 80 ton/fed, respectively, while they reached 2.33, 3.16, 4.26, 6.03, 7.36 and 8.60 kg/plot for town refuse ash additions at the same rates, respectively. Statistical analysis showed that a quadratic function fitted the relationships between either coal refuse or town refuse ash rates and sesame seed yield (r = 0.97**). Differential's method of quadratic equation obtained was used to find the predicted values of critical level of amendments rate. The value of the critical level was 127 ton/fed, as it represents the rate where further change in application results in a reduction in the yield.