In natural ecosystems, biological relationships have serious effects on system stability. Allelopathic is negative or positive effect of a plant on other plant growth. Today this word is used for rangelands, same as agricultural areas. Because of good herbage production, Medicago is most common plant in agricultural rotations and rangelands. Therefore investigation of its allelopathic qualities could help us to handle agricultural rotations or rangelands more properly. In this research after collecting alfalfa phytomass, we put them in oven in 40ºC, and then extract was produced at (0, 50 and 100℅ dilutions for leaves) and (0, 25, 50 and 100℅ dilutions for roots). In next step, by using complete randomized block with 5 replications, Trifollium sp and Beta Vulgaris seeds were mixed with extraction and put in germinator in 20 centigrade temperature and data was analyzed by Dunnett’s Test in SPSS Software. Results showed that materials completely inhibited germination and seedling growth of Trifollium sp and Beta Vulgaris.