Tow field experiment, were conducted  at El-Serw Agricultural Experiment Station, Damietta Governorate, to study the effect of phosphorus fertilizer levels ( 0, 15, 30 and 45 kg P₂O₅/fed.), potassium fertilizer levels (0, 24, 48 and 72 Kg K₂O/ fed.) and their combinations on cotton plant. Vegetative samples from the first full mature leaf were taken just preflowering to determine N, P and K concentrations.
          Some yield components (number of open bolls /plant, boll weight, seed plant index and oil with lint percentages) and cotton yield (seed cotton yield, seed yield, lint yield and oil yield) were determined.
Obtained results can be summarized as follows:
1- Phosphorus or potassium application increased significantly nitrogen, phosphorus and potassium concentrations in cotton leaves , while combination with each other did not significantly.
2- Number of open bolls/ plant , boll weight , seed index , oil percentage lint percentage ,seed cotton yield, seed yield, lint yield and oil yield were increased significantly by phosphorus or potassium application either alone or in combination with each other in both the two seasons ,while number of open bolls /plant was not affected significantly in the second season. The highest rate of phosphate (45 Kg P₂O₅ /fed.) and potassium (72 Kg K₂O/ fed.) recorded the maximum responses.
3- No significant differences were found between the highest two rates of P and K fertilizer on the above mentioned measurements.
4- Lint and oil percentages were correlated significantly with nitrogen , phosphorus and potassium concentrations.
5- It is concluded that application of (65 Kg N/ fed. + 30 Kg P₂O₅/fed.+48 Kg K₂O/fed.) was the best treatment  for cotton grown in salt affected soils in the north of Delta.