General gameplay tactics and its features.

Hmm. I wouldn't want to argue with an expert, but as far as I remember, with an Earth expert, the earth field lasts for 3 turns - the turn it was placed and 2 more full turns. With basic earth magic, it lasts for 2 turns. With advanced earth magic, I don't remember. That's why I wrote in the post that it disappears on the 4th (3rd) turn. I don't have the opportunity to test this right now, so try it yourself. Perhaps this applies to older versions; I don't remember anymore. :)