RESPONSE OF RUBBER (Hevea brasiliensis Mull. Arg) AT THE IMMATURE STAGE GROWTH TO VARIATIONS IN FERTILIZER APPLICATION

Abstract

Rubber (Hevea brasiliensis) is a commodity that plays a vital role in the Indonesian economy, although its productivity still lags behind that of competing countries. One factor contributing to low productivity is suboptimal cultivation practices, particularly during the nursery or immature plant phase. Proper fertilization is a key factor in producing high-quality seedlings. This study aimed to analyze the growth response of rubber seedlings to various combinations of inorganic fertilizer, biofertilizer, and liquid organic fertilizers (LOF), and to determine the most effective application rates. The experiment was conducted at the Ciparanje Experimental Field, Universitas Padjadjaran, from March to June 2025. A Randomized Complete Block Design (RCBD) was employed using nine-month-old rubber seedlings of clone PB 260, which were subjected to eight different fertilization treatments. Observed parameters included plant height, stem circumference, number of compound leaves, chlorophyll content, and leaf area. The results after three months of treatment showed that the application of the biofertilizer at 30 g per plant, combined with LOF at 6 mL.L⁻¹ produced the highest stem circumference growth and significantly increased plant height. Meanwhile, the treatment with biofertilizer at 10 g per plant combined with LOF at 6 mL.L⁻¹ resulted in the highest leaf area (638.8 cm²), which was statistically significant. The recommended dose of inorganic NPKMg fertilizer at 10 g per plant produced the best results for the number of compound leaves (10 leaves). It can be concluded that an integrated fertilization approach, particularly the combination of biofertilizer and LOF, is highly effective in supporting the vegetative growth of rubber seedlings, although the optimal dosage varies depending on the targeted growth parameters.