Bacterial inoculants and chemical additives are known for their positive effects on improving fermentation and prolonging the aerobic stability of silage. Alfalfa cut with an average dry matter of 37.3% was experimentally ensiled in special perforated bags, placed directly into the cut in the silage trough. The temperature was measured in the samples throughout the test. The negative control was silage without the use of a silage additive. A biological additive containing Lactiplantibacillus plantarum, Pediococcus pentosaceus, Enterococcus faecium in a dose of 1.5 g/t of silage and 3 g/t, as well as a chemical additive containing formic and propionic acid, sodium formate and sodium benzoate in a dose of 3 kg/t and 5 kg/t, was tested. The inoculant showed a statistically signifi cant (P < 0.01) better pH and NH3-N content than the control without the additive. The higher dose of inoculant had an effect only on increasing the ratio of lactic acid to volatile fatty acids. The chemical additive had a better result compared to the control only for NH3-N. A better result was obtained for the silage with a higher dose of additive, but the difference was minimal. For the entire 7 days, all tested silage variants were aerobically stable.