Production of Pelleted Organic Fertilizer from Swine Manure and Palm Oil Extraction Residues Using Dry Thermal Processes and Its Effects on Oil Palm (Elaeis guineensis L.) Seedling Growth

Abstract

This study aimed to evaluate the effects of microbial solutions LDD.1 and LDD.3 on adjusting the moisture content of organic fertilizer to 30% prior to the pelleting process. The investigation focused on their impact on essential plant nutrients, organic matter content, total viable microorganisms, and Trichoderma spp. counts. Additionally, the study assessed the efficiency of the pelletization process and the effects of organic fertilizer application rates on the growth and leaf color parameters (CIE L*, a*, b*) of oil palm seedlings (Elaeis guineensis L.). The results revealed that the application of LDD.1 and LDD.3 had no statistically significant effects on the levels of nitrogen, phosphorus, potassium, or organic matter in the pelleted fertilizer after storage at room temperature. Similarly, no significant differences were observed in pelleting efficiency, solubility, or the diameter of fertilizer pellets. However, the use of LDD.3, either alone or in combination with LDD.1, significantly increased the total viable microorganisms and Trichoderma spp. counts in the pelleted fertilizer (p < 0.05). The study further evaluated the impact of different organic fertilizer application rates on oil palm seedling growth and leaf color parameters for 60 days. The results revealed that the application of organic fertilizer significantly enhanced seedling growth. The highest seedling height was observed at an application rate of 50% by weight (w/w), based on the weight of organic fertilizer relative to the total weight of soil and fertilizer in the seedling bags. Organic fertilizer also significantly influenced the a* and b* color parameters, showing clear differences among treatment groups (p<0.05). Conversely, the L* parameter showed no significant differences. Fertilizer application reduced the redness parameter (a*) and decreased the yellowness parameter (b*), contributing to greener leaves. These findings highlight the potential of microbial-enriched pelleted organic fertilizer to enhance soil quality and plant growth, supporting the Zero Waste principle and the BCG model for sustainable agriculture.