Does metal oxidize (faster) in dirt? I had an interesting event occur recently: I stuck a screwdriver in a potted plant, for it is the only way that I am able to unlock a certain door. It was left in there for about a month before I needed it again, and, when I took it out, it had what I thought to be rust. I am doubting my original assumption.

I know for a fact that it is not dirt itself, as I vigorously attempted to clean it with suds (though I'm not entirely sure whether or not that was the best approach...).

Question

Does iron a) oxidize in dirt and b) if a), does it oxidize faster in dirt?
Iron can corrode faster in soil than in air, particularly if partly immersed in the soil. Moisture and electrolyte are retained in the soil, making it a good anode. Also, microbes in the soil can accelerate corrosion.