IMPROVING SQUASH (Cucurbita pepo L.) PLANT GROWTH, SEX EXPRESSION AND YIELD BY FOLIAR APPLICATION OF POTASSIUM AND ETHEPHON UNDER HIGH SUMMER TEMPERATURE CONDITIONS

This field experiment was carried out during the summer seasons of 2013 and 2014 to the Experimental Farm, Faculty of Technology and Development (Ghazala-Zagazig), Zagazig University, Sharkia Governorate, to study the response of squash plants cv.Revera to the foliar spray of potassium fertilization at the concentration of 1,2and 3ml l-1 as 37.5% K2O (four times) and ethephon (ethrel) at 150,250 and 350ppm( once at 2-4 true leaves stage) each alone or in combinations. The obtained results revealed that treated squash plants with foliar application of potassium and ethephon separately or in combination significantly influenced the studied characters compared to untreated plants in both seasons. However, spraying plants with 2 ml K2Ol-1+ 250 ppm ethephon gave the maximum values of most growth characteristics, i.e. number of leaves, fresh and dry weight per plant. Moreover, the treatment with 2 ml K2O l-1 +250 or 350 ppm ethephon recorded the best results of floral traits by decreasing the number of male flowers and sex ratio whereas increased number of female flowers, femaleness as well as yield and its components ,i.e. number of fruits /plant, fresh weight of fruit ,early and total yield per plot. Conclusively,from these results it could be concluded that foliar application of potassium at 2ml K2O l-1 +ethephon at 250 or 350ppm proved to be the best choice for growing and improving sex-expression by increasing number of female flowers and consequently the yield of plants when squash grown under high summer temperature condition (June , July and August).