Effectiveness of Zeolite and Humic Acid-Based Granular NPK Fertilizer on Durian (Durio zibethinus) Growth

Abstract

Improving the efficiency of NPK fertilizers can be achieved by incorporating materials such as zeolite and humic acid, which slow the release of nutrients. The objectives of this experiment is to evaluate the effects of a granular NPK fertilizer (6:6:12) enriched with zeolite and humic acid and compared with a standard commercial NPK fertilizer (15:15:15) on durian (Durio zibethinus) growth and determine optimal dosing. This experimental study arranged a two-factor Randomized Block Design (RBD): the first factor was fertilizer type (zeolite and humic acid-enriched NPK versus commercial NPK), and the second was fertilizer dose (300 g, 500 g, and 700 g per plant every three months). The study was conducted on two durian varieties, Musang King and Bawor, measuring growth parameters such as plant height, stem diameter, and number of primary branches. Soil chemical properties (pH, CEC, base saturation, C-dd, K-dd, N-add, Mg-dd, organic-C, EC, available P, available K, N-NH₄, and N-NO₃) were also observed. Results indicated no significant difference in growth between plants fertilized with zeolite and humic acid-enriched NPK and those treated with commercial NPK fertilizer. Optimal doses for Musang King and Bawor durian growth were found to be 500 g and 300 g per plant per three months, respectively. These findings highlight that, despite its lower NPK content, the zeolite and humic acid-enriched fertilizer enhances nutrient efficiency, likely through improved nutrient retention and gradual release.