Effect of three sowing dates of barely plants (Beginning of November, Middle of November and End of November) and different rates of potassium and nitrogen fertilizations on population density of some homopterous insects (aphid, leafhopper and planthopper) and crop yield during two successive seasons (2022/23 and 2023/24) was examined. The obtained results could be summarized as follows: 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 on the relative occurrence of the above mentioned insects since the highest mean number of insects occurred with F1treatment (zero potassium sulfate fertilizer),while the lowest mean number was recorded with F4treatment (100 kg. potassium sulfate/fedd.); c) Infestation by aphid, leafhopper and planthopper insects increased almost proportionality as  the added amount of nitrogen fertilizer increased; d) Chemical analysis of plant samples showed that there was a reverse relationship between protein and carbohydrate contents and density of the previously insects on all tested potassium fertilized barely plants, while a positive relationship between pH values and insect densities  was obtained; and f) the highest yield was obtained  when barely plants were early sown on the beginning of November in both seasons.