What type of fertilizers are considered slow-release?

Slow-release fertilizers are specifically designed to release nutrients gradually over an extended period. This slow release is crucial for minimizing nutrient loss to leaching, ensuring that plants receive a steady supply of nutrients that align with their growth needs. Controlled-release or coated fertilizers exemplify this concept perfectly. These fertilizers are coated with materials that slow down the nutrient release when applied to the soil. As the coating degrades or as soil moisture interacts with the fertilizer, nutrients are released at a rate that matches plant uptake, reducing the frequency of applications and enhancing nutrient efficiency.

In contrast, water-soluble fertilizers deliver nutrients quickly, often leading to rapid plant response but also potential nutrient leaching. Organic fertilizers, while beneficial for soil health and structure, often have varying release rates depending on microbial activity and environmental conditions, typically not designed as slow-release. Liquid fertilizers usually provide nutrients in a readily available form but do not offer the gradual nutrient release characteristic of slow-release fertilizer types.