The Effect of Nutrient Availability and Water Deficit on

The 2010 eruption of Mount Merapi acted as a natural scarification agent for Acacia decurrens seeds, enabling vigorous germination and dominance. Consequently, A. decurrens is considered to possess invasive potential despite its economic uses. This study aimed to assess A. decurrens seedlings' response to nutrient availability and water stress through fertilization and watering treatments. The experiment was conducted at Klebengan Greenhouse and Tree Physiology and Forest Soil Laboratory, Faculty of Forestry UGM, using a split-plot design. Watering treatments (main plot) included daily, every 4 and 7 days, while NPK fertilization doses (sub-plot) comprised 0, 1.5, and 3 g, each with five replications. After transplanting, seedlings received intended treatments and were observed for eight weeks. Measured parameters included seedling height, stem diameter, leaf number & color, root and shoot biomass. Data were analyzed using ANOVA and DMRT for mean comparison. The results showed that watering gave no significant effect on seedling height and diameter. However, it significantly affected shoot and root biomass, with the highest observed under daily watering, while no significant differences were found between seedlings watered every 4 and 7 days. These findings indicate that A. decurrens are relatively tolerant to drought. Regarding nutrient requirements, the best growth was achieved with 1.5 g of NPK, suggesting that seedlings do not require high nutrient inputs for optimal growth. The observations also found root nodules in seedlings without fertilization, with the highest number of root nodules observed in those with watering treatments of every 4 and 7 days. Thus, although seedling growth tended to decline under stress conditions, A. decurrens exhibited growth characteristics similar to those of invasive species, highlighting the need for proper management.