Two field experiments were conducted during 2015/2016 and 2016/2017 seasons at the Agricultural
Experimental Farm of Suez Canal University at Ismailia to study the effect of four phosphorus fertilization treatments
namely 15, 22.5, 30 and 15 Kg P2O5/fad plus biofertilizer phosphorein as well as four potassium fertilization treatments
namely 24, 48, 72 and 24 Kg K2O/fad plus spraying with 1% potassium sulphate on sunflower Sakha 53 variety in
sandy soils at Ismailia. Increasing phosphorus fertilization rate up to 30 Kg P2O5/fad significantly increased all
vegetative growth characters namely plant height, stem diameter, leaves area per plant, leaf area index and total dry
weight per plant in the two seasons. Applying biofertilizer phosphorein plus 15 Kg P2O5/fad reflected significant
increases in the above characters compared to 15 Kg P2 O5/fad alone in the two seasons. Increasing potassium
fertilization level up to 72 Kg K2O/fad significantly increased all vegetative growth characters in the two seasons.
Sunflower plants sprayed with 1% potassium sulphate plus 24 Kg K2O/fad exceeded significantly those fertilized by 24
Kg K2O/fad alone in all aforementioned characters in the two seasons. The highest values of all vegetative growth
characters produced from plants received 30 Kg P2O5/fad and 72 Kg K2O/fad in the two seasons.