This study was conducted at the Ataturk University’s farm in Erzurum over 2 years (2004-2005) to evaluate the effects of phosphorus doses and application season on the dry matter production, botanical composition and crude protein, ADF and NDF content of an alsike clover-dominated natural hay meadow. The experiment was planned in a Randomized Complete Block Design with split-plot arrangement of application seasons (autumn and spring) was considered as a main plot and five phosphorus doses (0, 11, 22, 33 and 44 kg P ha-1) as subplots. P fertilization significantly affected the dry matter yield while the application season had no effect on dry matter yield. P application increased the legumes and decreased the other families percentage in the botanical composition, whereas it did not affect the grasses percentage. Due to the nature of alsike cover, the proportion of the legumes decreased and the proportion of grasses increased significantly in the second year. P application had no effect on the crude protein and ADF content of hay, while NDF content was affected by both doses and the season of P application. Depending on changes in botanical composition between years, the chemical content of the hay changed between years. The results indicate that P fertilizer has positive effects on dry matter production and no serious effect on the forage quality of meadows and there are no significant differences between autumn and spring application. Therefore, an 11 kg ha-1 application of P in the spring can be suggested for sustainable dry matter production in legumes-dominated natural hay meadows in highland areas.