What is a key characteristic of soil permeability?

Soil permeability refers to the ability of soil to transmit water and air through its pore spaces. The key characteristic that defines soil permeability is how quickly water moves through the soil. This movement is influenced by factors such as the size and connectivity of soil particles, which determine the spaces through which water can flow. A soil with high permeability allows water to pass through quickly, while soil with low permeability retains water longer.

The other choices are related to soil properties but do not define soil permeability directly. Soil color can provide insights into organic matter content and drainage conditions, but it does not influence permeability. Nutrient content is impacted by various factors, including organic matter and pH, but again, it doesn't directly relate to the speed at which water moves through the soil. Organic matter levels can affect water holding capacity and soil structure, but they do not directly indicate how permeable the soil is. Therefore, the determination of water movement speed is the defining characteristic of soil permeability.