Alfalfa (Medicago sativa L.) is difficult to ensile due to high crude protein content (192 g/kg DM) and associated buffering capacity. A 4×2 factorial experiment (51-day continuous temperature monitoring) tested four preservation treatments (untreated control, enzymatic inoculant with hydrolytic enzymes, control inoculant without enzymes, formic acid) at 20 degrees C and 30 degrees C in three replicates. The enzymatic inoculant produced the most pronounced thermal response (+0.76 degrees C at 30 degrees C; Cohen’s d = 0.240) and the optimal fermentation profile (LA:VFA ratio 3.46 at 30 degrees C; VFA 2.50% DM), but exhibited the lowest aerobic stability at elevated temperature (31 h vs. 93 h for formic acid). Formic acid demonstrated minimal and temperature-independent dry matter losses (0.32-0.54%) with excellent aerobic stability across both temperature regimes. Significant treatment x temperature interactions were identified for VFA (F = 794.32; p < 0.001) and DM losses (F = 50.57; p < 0.001). The study reveals a fundamental trade-off between fermentation quality and aerobic stability with practical implications for seasonal optimization of alfalfa silage onservation.