In the conducted experiments the effect of presowing He-Ne laser light, magnetic field stimulation or the combination of these two factors of alfalfa seeds on the field emergence, structure and yields in the year of sowing and during three following years of full land use were studied. The examined factors had a significant effect on the number of shoots per 1 m², plant height, mass of shoots, fresh and dry mass. Electromagnetic stimulation resulted in a significant increase in alfalfa seeds emergence (from 35% – control to 47.8% – magnetic field), number of shoots per 1m2 (from 608 – control to 813 – laser light in cut), but a decrease of the mass of the shoots (from 0.61 g – control to 0.50 g – laser light).