Soil is a mixture of organic and inorganic materials, air, and water located between planet's lithosphere and atmosphere that supports life.
Omicron Theta was a farm planet but its soil bacteria was taken by the Crystalline Entity, making it useless. (TNG: "Datalore")
When Doctor Julian Bashir arrived at the Bajoran village he received a medical emergency message from he scanned the air, the water, and the soil but was not able to find any pollutants. (DS9: "The Storyteller")