The Effect of NPK–Zeolite Fertilizer on the Growth of Kopyor Coconut and Nutrient Availability in Ultisols of Tasikmalaya

Abstract

Ultisols in the Tasikmalaya region have low fertility, limited cation exchange capacity, and high nutrient fixation, which cause nutrient loss and restrict the growth of kopyor coconut. This study evaluated the effects of NPK-Zeolite fertilizer on vegetative growth and soil nutrient availability across different land-slope conditions. The research was conducted at PT Cigula Bumi Mineral, Tasikmalaya, from August to December 2024 using a 2×4 factorial Randomized Complete Block Design with two factors: fertilizer type (NPK-Zeolite and Conventional NPK) and land-slope classes (0–8%, 8–15%, 15–25%, >25%). Each treatment was replicated three times, resulting in 24 experimental units receiving 300 g of fertilizer per plant every three months. Data on vegetative growth and soil chemical properties were analyzed using ANOVA followed by DMRT at 5% significance. NPK-Zeolite increased ammonium availability to 76.72 ppm and potassium availability to 88.46 ppm, reflecting the slow-release characteristics of zeolite that reduced nutrient loss. However, plant height, stem diameter, and leaf number did not differ significantly between fertilizer types. Low soil phosphorus availability was likely the main factor limiting growth. Overall, NPK-Zeolite improved nitrogen and potassium efficiency in Ultisols, but additional measures are needed to overcome phosphorus deficiency.