Which factor is considered to have the greatest impact on soil resistivity?

Soil moisture is indeed considered to have the greatest impact on soil resistivity. The resistivity of soil affects how easily electrical currents can flow through it, and moisture plays a crucial role in this conductivity. When soil moisture levels are higher, the water present in the soil fills the voids between soil particles, allowing ions to move more freely. This increased ion mobility significantly enhances the soil's ability to conduct electricity, thereby reducing resistivity.

In contrast, dry soil, which has low moisture content, tends to have a higher resistivity because there are fewer ions available to carry the electrical current. This understanding is critical in lightning protection systems, where effective grounding is essential for safety and performance. The variations in moisture levels due to environmental changes can greatly influence the performance of grounding systems, making it vital to assess soil moisture in grounding applications effectively.