Two field experiments were conducted at Salheya area, Sharkia Governorate, Egypt during two seasons (2015 and 2016) to study the effect of N, K fertilization and irrigation systems on citrus trees (Citrus sinenis), in case of converting irrigation system from flood to pressurized irrigation systems. Two N rates (800 and 1000g N/tree/year) and K (330 and 500 g K/tree/year) in the experiment 1 using 8 pressurized irrigation systemsbeside flood irrigation. Three N rates (800, 1000 and 1200 g N/tree/year) and K (330,500 and 660 g K/tree/year) in experiment 2 under 6 irrigation systems using equal water amounts for all converted trees (25 m³/tree/year) by using small valves, and flood irrigation. 800 g N/tree/year and 330 g K/tree/year gave the highest N content in leaves in trees converted from flood to two lines dripper (S7), Highest K content in leaves was obtained by treatment of 1000 g N and 500 gK/tree/year under non converted trees (flood). In experiment 1, highest content of total soluble solids (TSS) was obtained by 800 g N and 500 g K under trees converted from flood to Micro Jet in circle shape (S5), and the highest acidity pH was obtained by treatment of 1000 g N and 500 g K under trees converted from flood to S7. In experiment 2 the highest N content in leaves was obtained by treatment of 1200 g N/tree/year and 660 g K/tree/year in converted trees to (S5) and the highest content of K in leaves was obtained by treatment of 1200 g N/tree/year and 330g K/tree in converted trees to T. dripper in square shape (S4). Application of 1000 g N/tree/year with 500 g K/ tree/year gave the highest percentage of TSS, and the highest percentage of total acidity was obtained due to adding of 1200 g N combined  with 330 g K/tree/year in converted trees from flood to (S5).