Two field experiments were carried out during the summer seasons of 2020 and 2021, to study the effects
of foliar application with various organic acids, i.e., ascorbic, salicylic, citric and fulvic acids as well as
the binary combination between them on vegetative growth parameters, chemical constituents, total fruit
yield, and fruit quality of squash plants cv. galaxy 555. This experiment included eleven treatments, (
T1- Ascorbic at 0.5 g/L, T2- Salicylic at 0.5g, T3- citric at 0.5g, T4-Fulvic at 0.5g, T5- Ascorbic at 0.5
g/L + Salicylic at 0.5g, T6- Ascorbic at 0.5 g/L + citric at 0.5g, T7- Ascorbic at 0.5 g/L + Fulvic at 0.5g,
T8- Salicylic at 0.5g+ citric at 0.5g, T9- Salicylic at 0.5g+ Fulvic at 0.5g, T10- citric at 0.5g + Fulvic at
0.5g and T11- Control). Results show that all foliar applications with organic acids treatments when used
either singly or combined on squash plants, significantly, increased all vegetative growth characters
(plant height, number of leaves/plant, plant fresh weight, plant dry weight and leaf area), chemical
constituents (Total chlorophyll, N, P, K), yield and its components ( Early yield per plant, number of
fruits per plant and total yield per plant) and fruit quality's characters (Average fruit weight, fruit length
and fruit diameter) comparing to non-treated plants during both seasons. Obtained results indicate that
foliar spray of ascorbic at 0.5 g/L+ salicylic at 0.5g (T5) or ascorbic at 0.5 g/L + citric at 0.5g (T6) is the
most effective on vegetative growth characters, the chemical composition of leaves, fruit yield and
quality of squash plants.