Influence of adding Eucalyptus litter and mixed litter on planting media to growth of Calliandra Seedlings (Calliandra calothyrsus)

The rapid depletion of fossil fuel reserves and the resulting environmental degradation have necessitated the transition to renewable biomass energy, such as wood pellets derived from Calliandra (Calliandra calothyrsus). The success of Calliandra cultivation as a raw material for bioenergy is highly dependent on the quality of the growth media during the early seedling stage. This research aimed to evaluate the effectiveness and growth response of Calliandra calothyrsus seedlings to the addition of Eucalyptus litter and mixed litter in the planting media. The research was conducted at the Forestry Management and Watershed Rehabilitation shading area of Bukit Asam Public Company using a one-factor Completely Randomized Design with five treatments: T0 (100% top soil), T1 (25% Eucalyptus litter + 75% top soil), T2 (50% Eucalyptus litter + 50% top soil), T3 (25% mixed litter + 75% top soil), and T4 (50% mixed litter + 50% top soil). Growth parameters, including plant height and the number of leaf stalks (petioles), were monitored over a 14-day observation period. Analysis of Variance (ANOVA) revealed that the treatments significantly influenced both seedling height (p = 0.0083, which is p < 0,05) and petiole production (p = 0.0000053, which is p < 0,05). Post-hoc Tukey’s HSD tests indicated that T4 (50% mixed litter) achieved the highest growth performance in height, while T3 (25% mixed litter) produced the greatest number of leaf stalks. The superior performance of mixed litter treatments is attributed to accelerated decomposition and mineralization rates, which enhance nutrient availability and soil porosity. Conversely, treatments involving Eucalyptus litter (T1 and T2) showed lower growth compared to the control. This inhibition is likely caused by the high lignin content of fresh Eucalyptus leaves, which slows decomposition, and the presence of allelopathic polyphenols that suppress cell division and mitotic activity. This research concludes that mixed organic litter is more effective for optimizing Calliandra calothyrsus seedling growth and recommends a longer decomposition period to neutralize allelopathic risks in Eucalyptus-based media.