Soil Properties and Potassium Dynamics Under the Influence of Organomineral Fertilization in a Tropical Sandy-loam Soil

Purpose Potassium (K) is essential for plant growth, yet most Brazilian soils are K-deficient, increasing reliance on imported mineral fertilizers. Organomineral fertilizers (OMF) combine organic residues with mineral nutrients and are a potential solution to reduce environmental impacts and improve K use efficiency. In this study we evaluated the release of K from OMF and its influence on the chemical, physical, and microbiological properties of a sandy loam soil. Methods A soil incubation study was conducted using columns filled with sandy loam soil treated with OMF and potassium chloride (KCl) for comparison. Miscible displacement tests were performed to assess K leaching, and basal soil respiration was measured to estimate microbial activity. Results OMF showed a slower and more gradual release of K over time compared to KCl. This slow release contributed to prolonged K availability and greater nutrient retention in the soil, delaying leaching losses. In addition, OMF increased microbial activity, indicating improved biological conditions in the soil. Conclusions OMF improve K retention and enhance microbial activity in sandy soils, demonstrating their potential to increase K use efficiency and reduce fertilizer losses. This study highlights K dynamics under miscible displacement conditions, integrating chemical, physical, and biological assessments rarely addressed together in previous research. Our results support the use of OMF as a sustainable strategy, aligned with the United Nations Sustainable Development Goals, especially in regions with low natural K reserves.