Formula of Pelletized Slow-Released Fertilizer Based on Pineapple Plant Stump Biomass Compost–Coal Fly Ash and its Recycling Application on Ananas Plantation

This study evaluates the performance of pelletized slow-release fertilizers (SRFs) formulated from pineapple plant stump biomass compost and coal fly ash at varying ratios, with the dual aim of enhancing soil nitrogen availability and promoting vegetative growth in pineapple, while valorising agricultural residue. A field trial was conducted from 2021-2022 in Lampung, Indonesia. Mineral fertilizers were encapsulated in emulsified polymer coatings at lower and higher coating concentrations. Pelletized SRF treatments were arranged in a randomized complete block design for control and various compositions of compost + fly ash. Soil N status was monitored periodically via total N, nitrate (NO₃⁻), and ammonium (NH₄⁺) assays, alongside measurements of N losses through leaching and volatilization. Vegetative responses were quantified by leaf count, leaf area index, and root biomass at 30 days after transplanting. All SRF treatments improved soil N availability relative to the control, with the 40% compost formulations, especially at high coating concentrations, exhibiting the best soil N status. These high-compost SRFs also delivered potential gains in root biomass and foliar development, which can be attributed to the enhanced soil organic matter. The results demonstrate that pineapple stump–fly ash SRFs can simultaneously recycle biomass waste and sustainably boost nutrient efficiency and plant growth in pineapple cultivation.