Effectiveness of zeolite and humic acid-based granular NPK fertilizer on durian (

Improving NPK fertilizer efficiency can be achieved by incorporating zeolite and humic acid to slow nutrient release. This experiment evaluated the effects of a granular NPK fertilizer (6:6:12) enriched with zeolite and humic acid compared to a standard commercial NPK fertilizer (15:15:15) on durian (Durio zibethinus) growth and determined optimal dosing. A two-factor Randomized Block Design (RBD) was used: the first factor was fertilizer type (enriched NPK vs. commercial NPK), and the second was fertilizer dose (300 g, 500 g, and 700 g per plant every three months). The study, conducted on Musang King and Bawor durian varieties, measured growth parameters (plant height, stem diameter, and number of primary branches) and soil chemical properties (pH, CEC, base saturation, organic-C, and nutrient availability). Results showed no significant growth difference between plants fertilized with enriched and commercial NPK fertilizers. Optimal doses were 500 g and 300 g per plant per three months for Musang King and Bawor, respectively. Despite its lower NPK content, the enriched fertilizer improved nutrient efficiency through better retention and gradual release. These findings highlight its potential as a sustainable alternative for durian cultivation.