Which characteristic is affected by the size of soil particles?

The retention of moisture and permeability of soil are both influenced by the size of soil particles, but permeability is particularly dependent on particle size. Soil particles vary in size from clay, which is very fine, to sand, which is larger.

When soil consists of larger particles, there are greater spaces (pores) between them, allowing water to flow through more easily. This results in higher permeability, meaning that water can move through the soil at a faster rate. Conversely, smaller particles, such as clay, have very tiny spaces and can hold water tightly, which can lead to lower permeability.

So, while retention of moisture refers to how water is held within the soil, and it can be significantly influenced by particle size as well, it is the permeability that is more directly impacted by the connectivity and size of the pore spaces between soil particles. Thus, the characteristic most directly and clearly affected by the size of the soil particles is permeability.