A field trail was conducted at three sites in East Delta Region, Egypt, during the two successive summer seasons 2015 and 2016 as well as winter seasons 2015/2016 and 2016/2017 to study the physiological response of some field crops grown under saline soil conditions to foliar spraying with potassium at 1 and 2% K₂O in the form of K-leaf fertilizer besides control treatment. Results indicated that plant height, leaf area index (LAI), crop growth rate (CGR), net assimilation rate (NAR), photosynthetic pigments, soluble sugars, potassium content in leaves, potassium and protein percentages in grains or seeds, as well as yield and yield components for all crops under study were significantly increased when plants received 1% or 2% K₂O. Also, significant increase was achieved in proline, Na⁺, and Na⁺/K⁺ ratio in leaves when plants sprayed with water (control) as compared with other potassium treatments for all crops wheat, barley, faba bean, rice, maize and clover. Foliar spraying with 2% K₂O as K-leaf fertilizer was more efficient for increasing growth, biochemical, potassium percentage, protein percentage and yield of wheat, barley, faba bean, rice, maize and clover crops as compared to untreated potassium fertilizer (control) under saline soils conditions.