Three sowing dates of barely plants (Beginning of November, Middle of November and End of November) and different rates of potassium and nitrogen fertilizations were also used to show their effect on the population density of dominant homopterous insects (aphid, leafhopper and planthopper) as well as yield obtained during two successive seasons 2022/23 and 2023/24 The obtained results pointed out that: a) Sowing dates had a significant effect on the incidence and rate of infestation of barely plants by the aforementioned insects. b) Potassium and nitrogen fertilizations of barely plants influenced the relative occurrence of the above mentioned insects, the highest mean number of insects occurred with F1(zero potassium sulfate fertilizer) treatment, while the lowest mean number was recorded with F4 (100 kg. potassium sulfate/fedd.) c) The infestation by aphid, leafhopper and planthopper insects increased almost proportionality to the increase in the amount of nitrogen fertilizer added, d) Chemical analysis showed that a reverse relationship between protein and carbohydrate contents and the previously insects population on all tested potassium fertilized barely plants ,while a positive relationship between PH values and the studied insects population was obtained. f) The highest yield was recorded when barely was early sown on the beginning of November in both seasons.