1. Accessibility to plants: Plants can't directly absorb nutrients from solid particles. They need the nutrients dissolved in water to be able to take them up through their roots.

2. Movement within the soil: Water carries dissolved nutrients throughout the soil, allowing them to reach the roots.

3. Efficiency and uptake: Solubility ensures that the nutrients are readily available for the plant to absorb. If the fertilizer isn't soluble, the plant will struggle to access the nutrients, even if they are present.

4. Uniform distribution: A soluble fertilizer dissolves evenly in the soil water, ensuring that the nutrients are spread out and available to all parts of the root system.

5. Faster action: Soluble fertilizers are quickly absorbed by the plant, leading to a faster response in growth and development.

It's important to note that not all fertilizers need to be completely soluble in water. Some fertilizers are designed to release nutrients slowly over time, which can be beneficial in preventing nutrient loss and ensuring a steady supply to the plants. However, the solubility of the fertilizer is a crucial factor in its effectiveness.