A review on slow-release fertilizer: Nutrient release mechanism and agricultural sustainability

The increasing need for food to support the growing population has led to the widespread use of synthetic fertilizers in the agricultural sector around the world. Most of these conventional fertilizers are inefficient as they are readily water-soluble and quickly dissolve in the irrigation water or soil moisture, yielding excessive concentrations of the nutrients in the root zone, which the plants cannot uptake. Traditional fertilizers thus cause excess nutrients in the soil that harm the environment through processes like surface run-off, denitrification, volatilization, and nutrient loss via leaching, ultimately affecting human health directly and indirectly. Slow-release fertilizers offer a promising solution to address these issues. They allow for precise control over the release of chemical contents of fertilizers, improving nutrient use efficiency and reducing environmental pollution. The controlled chemical contents of the fertilizers can promote sustainable agriculture and enhance agricultural productivity. These fertilizers are ideally biodegradable, reducing emissions and toxicity. They must possess a high water-holding capacity, promote soil microorganisms' growth, enhance the yield and quality of agricultural products. This review provides a comprehensive overview of the various slow-release fertilizer compositions, preparation techniques including their advantages and disadvantages. This study also discusses the impact of organic, inorganic, and hydrogel-based fertilizers on nutrient-release behaviors. Parameters influencing the slow-release pattern such as temperature, pH, soil texture, coating thickness, microbial activity, and soil moisture have also been discussed. This review article provides a comprehensive and up-to-date overview of the latest advancements in slow and sustained-release fertilizer for modern agriculture and its future potential.