This work was conducted at a private farm in El-Kasr city, El-Dakhla Oasis, New Valley Governorate, during 2022 and 2023 seasons to study the effect of two sowing dates (1^st and 20^th February), foliar spray with some safe materials, i.e., salicylic acid (SA) at 0.5 and 1.0 mM, ascorbic acid (AsA) at 50 and 100 ppm, and potassium silicate (KSil) at 4 and 8 ml/l, beside untreated control, and the interaction between them on growth, yield and fruit quality of watermelon (cv. Aswan F1). The interaction between sowing watermelon on 20^th Feb. and foliar spray with KSil at 8 ml/l recorded the highest values of vegetative growth parameters and dry weight/plant, nitrogen, phosphorus and potassium content in leaves and average fruit weight, fruit quality, i.e., total soluble solids, total and reducing sugars, lycopene concentration and ferric reducing antioxidant power assay. While the interaction between sowing on 20^th Feb. and spraying plants with AsA at 50 ppm gave the highest total yield/feddan without significant differences in the interaction between sowing at the same date and spraying plants with KSil at 8 ml/l in both seasons. The relative increase in total yield/feddan were about 71.96 and 70.93% for the interaction between sowing on 20^th Feb. and spraying plants with KSil at 8 ml/l and 73.83 and 72.40% for the interaction between sowing on 20^th Feb. and spraying plants with AsA at 50 ppm over sowing date on 1^st Feb. and spraying plants with distilled water in the 1^st and 2^nd seasons, respectively.