To investigate the effect of commonly used chemical fertilizers on certain quantitative and qualitative characteristics of Khatouni melon ecotype, an experiment was conducted in a randomized complete block design at the research farm of Ferdowsi University of Mashhad. The treatments included: T1: control (no fertilizer applied), T2: nitrogen fertilizer from urea at a rate of 120 kg/ha, T3: phosphate fertilizer from triple superphosphate at a rate of 120 kg/ha, and T4: potassium fertilizer from potassium sulfate at a rate of 100 kg/ha. Results indicated that the use of potassium fertilizer led to a 17% increase in melon fruit length compared to the control. The application of fertilizers T2 and T3 resulted in a 14% and 15.5% increase in fruit length, respectively, compared to the control. The fruit lengths for treatments T2, T3, and T4 were 38 cm, 38.6 cm, and 39.3 cm, respectively. The highest middle diameter of the melon (14.5 cm) was obtained from treatment T3 and the lowest from treatment T1. The number of seeds per fruit was 649 in the control, with a 3% and 6% increase observed with T2 and T4 treatments, respectively. The highest and lowest flesh thickness were recorded from treatments T2 (3.66 cm) and T1 (3.00 cm), respectively. The highest (3.16 kg) and lowest (1.97 kg) fruit weights were obtained from treatments T4 and T1, respectively. Treatment T2 resulted in a 33% increase in fruit weight compared to the control. The highest positive and significant correlation was found between single fruit weight and fruit length (r=0.82*) and middle diameter (r=0.82*). The highest sugar content was observed in treatments T2 and T4.

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